Leaf Decomposition Research Articles

Dry weight loss in leaves of dominant species in a successional sequence of the Mesopotamian Espinal (Argentina)

Aim of study: To compare litter decomposition dynamics among different species within a single forest type and also between a single species in different forest successional stages.Area of study: Different forests of a known successional sequence of the Mesopotamian Espinal, placed in Villaguay Department, Entre Ríos Province, Argentina.Material and methods: A standard “litter bags” technique was employed. Chemical analyses of C and N were performed for leaves. A regression analysis was applied and data were fitted to a double exponential model. Means estimated among forests and species within each forest were compared using the Tukey-Kramer test.Main results: The model predicted that leaves would completely mineralize in the mid-term. Leaf decomposition rate in different species (both in the Secondary forest and Mature forest) had dry matter residues in the following decreasing order: Acacia caven > Prosopis nigra > Prosopis affinis > Celtis ehrenbergiana. Research highlights: Successional stage was not found to be a factor determining the decomposition rate among species. Different decomposition rates, observed among different species, would not be attributed to initial quality of residues in terms of C and N, but would be associated with a positive feedback process related to nutrient cycle; thus, a greater decomposition would increase nutrient availability and, consequently, litterfall input.

Differences in the decomposition of green and senescent leaves in streams of Reserva Florestal Adolpho Ducke (Amazonas, Brazil)

Leaves are considered the main energetic resource supply among all the allochthonous organic material available for the small shaded streams. However, their processing is limited by the physical and chemical characteristics of the leaves. Therefore, this research aimed to: i) evaluate the difference in decomposition coefficients between green and senescent leaves; ii) compare richness and density of aquatic invertebrates colonizing decomposing green and senescent leaves. Between November 2012 and January 2013, 12 leaf packages (6 senescent and 6 green) of 14 plant species were installed in 3 streams of the Reserva Florestal Adolpho Ducke (Manaus/AM - Brazil). After 15, 30 and 60 days the submerged packages were removed. The collected material was taken to the laboratory for analyzes of: aquatic invertebrates and leaves' mass remnants. Paired t-test was performed to verify if the decomposition coefficients (k) differed. ANCOVAs were performed to compare: the remaining mass (%), richness and density of aquatic invertebrates between leaf type over time. The green leaves presented higher leaf decomposition rates than in senescent ones. The leaf type influenced the average invertebrates densities. Therefore, green leaves were more susceptible to the colonization of aquatic invertebrates associated with the leaf decomposition process in small Amazonian streams.

Combined effects of insecticide exposure and predation risk on freshwater detritivores.

Insecticides usually present in low concentrations in streams are known to impair behaviour and development of non-target freshwater invertebrates. Moreover, there is growing awareness that the presence of natural stressors, such as predation risk may magnify the negative effects of pesticides. This is because perception of predation risk can by itself lead to changes on behaviour and physiology of prey species. To evaluate the potential combined effects of both stressors on freshwater detritivores we studied the behavioural and developmental responses of Chironomus riparius to chlorantraniliprole (CAP) exposure under predation risk. Also, we tested whether the presence of a shredder species would alter collector responses under stress. Trials were conducted using a simplified trophic chain: Alnus glutinosa leaves as food resource, the shredder Sericostoma vittatum and the collector C. riparius. CAP toxicity was thus tested under two conditions, presence/absence of the dragonfly predator Cordulegaster boltonii. CAP exposure decreased leaf decomposition. Despite the lack of significance for interactive effects, predation risk marginally modified shredder effect on leaf decomposition, decreasing this ecosystem process. Shredders presence increased leaf decomposition, but impaired chironomids performance, suggesting interspecific competition rather than facilitation. C. riparius growth rate was decreased independently by CAP exposure, presence of predator and shredder species. A marginal interaction between CAP and predation risk was observed regarding chironomids development. To better understand the effects of chemical pollution to natural freshwater populations, natural stressors and species interactions must be taken into consideration, since both vertical and horizontal species interactions play their role on response to stress.

中国温带和亚热带8个树种叶和吸收根协同分解

PDF HTML阅读 XML下载 导出引用 引用提醒 中国温带和亚热带8个树种叶和吸收根协同分解 DOI: 10.5846/stxb201704110634 作者: 作者单位: 山东省科学院海洋仪器仪表研究所,山东省科学院海洋仪器仪表研究所,山东省科学院海洋仪器仪表研究所,山东省科学院海洋仪器仪表研究所,山东省科学院海洋仪器仪表研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31300414，41406104） A coordinated decomposition between leaf litter and absorptive roots across eight temperate and subtropical tree species in China Author: Affiliation: Institute of Oceanographic Instrumentation,Shandong Academy of Sciences,Institute of Oceanographic Instrumentation,Shandong Academy of Sciences,Institute of Oceanographic Instrumentation,Shandong Academy of Sciences,Institute of Oceanographic Instrumentation,Shandong Academy of Sciences,Institute of Oceanographic Instrumentation,Shandong Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:叶和细根（ < 2mm）是森林生态系统的分解主体，二者是否协同分解，将极大影响所属植物在生态系统碳（C）循环中的物种效应。已有研究显示，叶和细根的分解关系具有极大的不确定性，认为很大程度上归因于细根内部具有高度的异质性，导致叶和细根在功能上不相似。为此，使用末梢1级根和细根根枝作为研究对象，它们在功能上同叶类似，称为吸收根。通过分解包法，分别在黑龙江帽儿山和广东鹤山，研究了2个阔叶树种和2个针叶树种（共8个树种）的叶和吸收根持续2a多的分解。结果发现，分解速率k（a-1，负指数模型）在8个树种整体分析时具有正相关关系（P < 0.05），在相同气候带或植物生活型水平上是否相关，受叶的分解环境及吸收根类型的影响；N剩余量整体上并不相关，亚热带树种的叶和细根根枝的N剩余量在分解1a后高度显著正相关，温带树种的叶和1级根的N剩余量在分解2a后显著高度正相关。本研究中，根-叶分解过程是否受控于相同或相关的凋落物性质是决定根-叶分解是否相关的重要原因，其中分解速率与酸溶组分正相关、与酸不溶组分负相关。比较已有研究，总结发现，根-叶分解关系受物种影响较大，暗示气候变化导致物种组成的改变将极大影响地上-地下关系，也因此影响生态系统C循环。 Abstract:Leaves and fine roots ( < 2mm) account for the majority of annual litter production in forests. Whether their decomposition is coordinated would largely influence species effects on terrestrial ecosystem C cycling. Currently, the relationship between leaf and root decomposition is still highly uncertain, which may be caused by the ambiguous and arbitrary definition of fine roots. Within fine roots, only the distal root tips (R1) or root branches (R1-3) are functionally comparable to leaves as resource acquisition organs (absorptive roots). Here, we investigated decomposition of leaf litter and absorptive roots using litter bags for two years across eight temperate and subtropical tree species in China. Results showed that decay rates k (a-1, negative exponential model) were positively correlated between leaf litter and absorptive roots when all eight temperate and subtropical trees were examined in combination, but when tree species were separated by climate zones or growth forms, the correlation was influenced by the soil depth at which leaf litter decomposition occurred, and the type of absorptive roots. N remaining in the leaf and root was not correlated when all eight trees were examined in combination. However, N remaining in the leaf and root was highly and positively correlated between leaf and R1-3 among subtropical trees after one year of decomposition, and between leaf and R1 among temperate trees after two years of decomposition. Here, the correlation between the decomposition of leaf and root was mainly influenced by whether both leaf and root decomposition were controlled by the same or related litter chemistry. In this study, all litter decay rates were positively related to acid soluble C fractions, but negatively related to acid insoluble C fractions. Summarizing results from our study and other studies, we found that the relationship between leaf and root decomposition was largely affected by species. Therefore, species composition dynamics due to climate change would largely affect above-and below-ground relationships and thus ecosystem C cycling. 参考文献 相似文献 引证文献

Food consumption of the invasive amphipod Dikerogammarus villosus in field mesocosms and its effects on leaf decomposition and periphyton

Food consumption of the invasive amphipod Dikerogammarus villosus in field mesocosms and its effects on leaf decomposition and periphyton

Contribution of aquatic shredders to leaf litter decomposition in Atlantic island streams depends on shredder density and litter quality

It has been widely reported that shredders play an important role in leaf decomposition, especially in continental temperate streams. However, the paucity of shredders in many oceanic island streams leads to a greater contribution of microbes to litter decomposition in these streams. In this study, we investigated the importance of shredder presence and density (three levels) and leaf litter identity (Alnus glutinosa, Clethra arborea and Acacia melanoxylon) on leaf litter decomposition in one stream located in the Azores Archipelago. Coarse and fine mesh bags were used to allow natural colonisation of leaf litter by benthic macroinvertebrates or to exclude macroinvertebrates respectively. Treatments with one and three shredders were accomplished by enclosing one or three shredders in the fine mesh bags. Rates of litter decomposition differed significantly among shredder density treatments only for A. glutinosa and C. arborea. Decomposition rates were significantly faster for the natural within-stream shredder density treatment than for other shredder treatments. Shredder density differed significantly among litter species, being higher in A. glutinosa than in C. arborea and A. melanoxylon. The results indicate that when shredders are present at high densities in oceanic island streams they can substantially contribute to the decomposition of high-quality leaf litter, whereas the decomposition of hard leaf litter is mostly performed by the microbial community.

Evaluating the effect of macroinvertebrate exclusion on leaf breakdown rates in two upland Colombian streams

Macroinvertebrate shredders have been widely recognized as an important functional feeding group that contributes to leaf decomposition in temperate streams, but little is known about their role in upland Neotropical streams. In this study, we investigated the effect of macroinvertebrate exclusion on leaf breakdown rates in two upland streams (Marianela and Peña Bonita with 1 911 and 2 560 m elevation, respectively) in Colombia. We hypothesized that leaf litter breakdown is mediated mainly by macroinvertebrate shredders in Colombian upland streams. The study was carried out between January and April of 2009, including the dry season and the beginning of the wet season. We measured leaf mass loss using coarse- (15 mm; accessible to macroinvertebrates) and fine- (200 µm; macroinvertebrates excluded) mesh litter bags that were anchored with wood stakes to the bottom of each stream and recovered after 7, 14, 21, 28, and 56 days. We selected leaves from two dominant plant species and used three leaf treatments: two single species (Palicourea cuatrecasasii and Critoniopsis ursicola) and mixed-species (P. cuatrecasasii and C. ursicola). We compared leaf breakdown rates between the Peña Bonita and Marianela stream, mesh-sizes, and leaf treatments. Macroinvertebrates that colonized the litter bags were measured for density and biomass and categorized in functional feeding groups. In general, there were no significant differences in breakdown rates between the streams and the mesh-sizes. In contrast, leaf breakdown rates had significant differences between all leaf species, where C. ursicola had higher breakdown rates than mixed-species, and P. cuatrecasasii. Macroinvertebrate exclusion did not affect leaf breakdown rates and their assemblages were composed by high densities of collectors (mainly Chironomidae) and few shredders with a large body size. The similar macroinvertebrate colonization between leaf species, the relatively slow breakdown rates, and the shredder scarcity, suggest that leaves were a refractory substrate. Further studies should include leaf species with different nutritional qualities and larger spatial-temporal scales to test the hypothesis of shredder presence and its role on leaf decomposition in upland Colombian streams.

Chlorpyrifos interacts with other agricultural stressors to alter stream communities in laboratory microcosms.

Chlorpyrifos is one of the most widely used agricultural insecticides in the world, but to date there is limited empirical information about its potential to interact with other common agricultural stressors. We conducted a 15-d, community-level, microcosm experiment evaluating individual and combined effects of chlorpyrifos, nutrient enrichment, and sedimentation on stream invertebrate communities (abundance, biomass, richness, size structure, composition) and ecosystem processes (primary productivity and leaf decomposition). We found that sedimentation was the most detrimental stressor, with significant negative impacts on most invertebrate community and ecosystem function variables. Even though chlorpyrifos did not cause significant invertebrate mortality in the microcosms, it still altered ecosystem function by lowering leaf decomposition rates, probably through sublethal inhibition of invertebrate shredders. Furthermore, we observed a significant reversal interaction between chlorpyrifos and sediment for small-sized invertebrates collected in gravel (abundance in sediment×insecticide microcosms was 2.4 times lower than predicted by additivity), as well as an antagonistic interaction with nutrients on invertebrate richness in the same microhabitat (richness in nutrient×insecticide microcosms was 1.6 times higher than predicted by additivity). Our results suggest that chlorpyrifos has the potential to alter freshwater ecosystem function and interact non-additively with other common agricultural stressors. These findings are in keeping with a growing body of research highlighting that multiple stressor interactions and ecosystem processes should be considered when evaluating the impacts of organic toxicants on freshwater ecosystems.

Microbial decomposition is highly sensitive to leaf litter emersion in a permanent temperate stream

Drought frequency and intensity in some temperate regions are forecasted to increase under the ongoing global change, which might expose permanent streams to intermittence and have severe repercussions on stream communities and ecosystem processes. In this study, we investigated the effect of drought duration on microbial decomposition of Populus nigra leaf litter in a temperate permanent stream (Oliveira, NW Portugal). Specifically, we measured the response of the structural (assemblage composition, bacterial and fungal biomass) and functional (leaf litter decomposition, extracellular enzyme activities (EEA), and fungal sporulation) parameters of fungal and bacterial communities on leaf litter exposed to emersion during different time periods (7, 14 and 21d). Emersion time affected microbial assemblages and litter decomposition, but the response differed among variables. Leaf decomposition rates and the activity of β-glucosidase, cellobiohydrolase and phosphatase were gradually reduced with increasing emersion time, while β-xylosidase reduction was similar when emersion last for 7 or more days, and the phenol oxidase reduction was similar at 14 and 21days of leaf emersion. Microbial biomass and fungal sporulation were reduced after 21days of emersion. The structure of microbial assemblages was affected by the duration of the emersion period. The shifts in fungal assemblages were correlated with a decreased microbial capacity to degrade lignin and hemicellulose in leaf litter exposed to emersion. Additionally, some resilience was observed in leaf litter mass loss, bacterial biomass, some enzyme activities and structure of fungal assemblages. Our study shows that drought can strongly alter structural and functional aspects of microbial decomposers. Therefore, the exposure of leaf litter to increasing emersion periods in temperate streams is expected to affect decomposer communities and overall decomposition of plant material by decelerating carbon cycling in streams.

Janzen–Connell patterns can be induced by fungal‐driven decomposition and offset by ectomycorrhizal fungi accumulated under a closely related canopy

Abstract Seedlings near a conspecific adult might suffer increased mortality due to pressure from enemies such as below‐ground pathogenic fungi (Janzen–Connell hypothesis), however, variation exists among taxa such that some experience low levels of mortality. We hypothesized that seedlings close to adults might profit, rather than suffer, from below‐ground fungi, notably from mycorrhiza or decomposers, in particular near large adult trees and under a closely related canopy. We planted oak seedlings in a temperate forest at different distances from adults and followed seedling mortality, budburst (early budburst permitting photosynthesis during the best light conditions) and leaf herbivory. We applied fungicide on half of the seedlings for 2 years to identify the net effect of below‐ground fungi on seedlings. We quantified seedling mycorrhization and fungal‐driven decomposition of a neighbourhood‐specific and an unspecific substrate, local oak leaves and cellulose respectively. Finally, we related mycorrhization and decomposition to seedling performance. We found that, in seedlings planted close to conspecific adults, below‐ground fungi had a negative net effect on seedlings: elimination of fungi, surprisingly, decreased herbivory. This effect could be due to oak leaf decomposition, which was related to increased seedling herbivory and was higher near a conspecific adult. Under a closely related canopy, however, the net effect of below‐ground fungi on nearby seedlings became positive: elimination of fungi delayed budburst. This effect could be due to colonization by the ectomycorrhizal fungus Cortinarius sp., which related to accelerated budburst and was higher near a conspecific under a closely related canopy. Effects of below‐ground fungi on nearby seedlings were not dependent on the size of the conspecific and were species but not lineage specific. Overall, our results suggest that a Janzen–Connell‐like pattern, that is, increased mortality of seedlings near conspecific adult, can be (1) induced by specialist decomposers increasing the nutritional quality of conspecific seedlings to herbivores, and (2) offset by ectomycorrhizal fungal mutualists under a closely related canopy. Coexistence among closely related adult trees appears to change interactions between adults and nearby conspecific seedlings from conspecific inhibition to conspecific facilitation. A plain language summary is available for this article.

Fungal plant pathogens on inoculated maize leaves in a simulated soil warming experiment

Climate change will affect the survival of plant pathogens and the decomposition of crop residues on temperate arable soils. Information on the survival of fungal plant pathogens is important for assessing the subsequent infection risk of susceptible agricultural crops. Therefore, a soil warming experiment was performed to examine the effects of rising winter soil temperatures on the inoculum load of fungal plant pathogens (Fusarium culmorum, F. graminearum, Rhizoctonia solani) and the decomposition of infested maize leaves under field conditions. Using heating cables, an arable soil was subjected to temperature treatments simulating medium (+1.3°C up to the year 2050) and long-term (+2.7°C up to the year 2100) climate warming scenarios. Litterbags filled with pathogen-inoculated and non-inoculated maize leaves were placed on top of the soil. Soil microbial biomass below the litterbags, maize leaf decomposition as well as microbial colonisation of leaves were measured after 152days. Pathogen load was estimated by DNA, total saprotrophic biomass by fungal glucosamine and bacterial muramic acid. Rising soil temperatures increased decomposition of pathogen-infested, but not that of non-inoculated maize leaves, without correlation to fungal and bacterial biomass. F. culmorum DNA produced the largest increase in DNA on maize leaves, but did not significantly respond to soil temperatures. In contrast, the increase in F. graminearum DNA was considerably lower, but revealed a significant positive response to rising soil temperatures. DNA from mycelia and sclerotia of R. solani strongly decreased. Rising winter soil temperatures will most likely cause shifts within the plant residue colonizing fungal community, especially between different Fusarium species.

Invasive Andropogon gayanus (Gamba grass) alters litter decomposition and nitrogen fluxes in an Australian tropical savanna

The African grass Andropogon gayanus Kunth. is invading Australian savannas, altering their ecological and biogeochemical function. To assess impacts on nitrogen (N) cycling, we quantified litter decomposition and N dynamics of grass litter in native grass and A. gayanus invaded savanna using destructive in situ grass litter harvests and litterbag incubations (soil surface and aerial position). Only 30% of the A. gayanus in situ litter decomposed, compared to 61% of the native grass litter, due to the former being largely comprised of highly resistant A. gayanus stem. In contrast to the stem, A. gayanus leaf decomposition was approximately 3- and 2-times higher than the dominant native grass, Alloteropsis semilata at the surface and aerial position, respectively. Lower initial lignin concentrations, and higher consumption by termites, accounted for the greater surface decomposition rate of A. gayanus. N flux estimates suggest the N release of A. gayanus litter is insufficient to compensate for increased N uptake and N loss via fire in invaded plots. Annually burnt invaded savanna may lose up to 8.2% of the upper soil N pool over a decade. Without additional inputs via biological N fixation, A. gayanus invasion is likely to diminish the N capital of Australia’s frequently burnt savannas.

Combined effects of predation risk and food quality on freshwater detritivore insects

Because both predation risk and resource quality have a pivotal role in ecological communities, their combined effects were assessed in stream detritivores. Bioassays were conducted using a simplified trophic chain, coupling effects of predation risk and basal resources with different nutritious qualities, namely, a predator planarian Dugesia subtentaculata, a caddisfly shredder Sericostoma vittatum, a dipteran collector Chironomus riparius, native alder Alnus glutinosa and invasive eucalypt Eucalyptus globulus. We investigated whether individual performance of C. riparius larvae is affected under predation risk and whether the response can be mediated by resource quality. We also assessed whether shredder–collector interactions are altered under these conditions. Predation risk and food quality influenced leaf decomposition and C. riparius growth independently. Chironomus riparius fed preferentially on alders, resulting in increased growth rate. Litter processing decreased under planarian presence, in both leaf types, impairing the growth of C. riparius larvae, this effect being exacerbated with eucalypts. Chironomus riparius growth was also reduced in the presence of the caddisfly, suggesting competition between these species, irrespective of planarian presence, but dependent on leaf type. The present study highlighted the importance of assessing predator influence along detritus-based processing chains, because predation risk may result in sublethal costs, with potential cascading effects.

Short-term root and leaf decomposition of two dominant plant species in a Siberian tundra

In tundra ecosystems, global warming is expected to accelerate litter decomposition and to lead to shifts in vegetation composition. To understand these shifts, it is important to understand the interactions between global warming, vegetation composition, litter quality and decomposition in the tundra. In addition, it is important to consider root litter since roots are the major part of plant biomass in the tundra. In order to increase our understanding of decomposition, and root decomposition in particular, we performed a litter transplant experiment in northeastern Siberia, in which we measured mass loss for leaf and root litter (live and dead material) of the two dominant plant species, graminoid Eriophorum vaginatum and shrub Betula nana, in three vegetation types (E. vaginatum or B. nana dominated and mixed vegetation) during the growing season.Our results show that although leaf decomposition did not differ between the two species, root decomposition showed significant differences. Mass loss of live roots was higher for E. vaginatum than for B. nana, but mass loss of E. vaginatum dead roots was lowest. In addition, we found evidence for home-field advantage in litter decomposition: litter of a plant decomposed faster in vegetation where it was dominant. Mass loss rates of the litter types were significantly correlated with phosphorus content, rather than nitrogen content. This indicates that phosphorus limits decomposition in this tundra site.The low decomposition rate of B. nana live roots compared to E. vaginatum live roots suggests that the acceleration of decomposition in the Arctic may be partly counteracted by the expected expansion of shrubs. However, more information on litter input rates and direct effects of climate change on decomposition rates are needed to accurately predict the effects of climate change on carbon dynamics in tundra ecosystems.

Linking riparian forest harvest to benthic macroinvertebrate communities in Andean headwater streams in southern Chile

Headwater streams are fully linked to surrounding riparian vegetation through coarse and fine organic matter inputs. However, forestry operations in or close to riparian corridors, particularly in mountainous forested microcatchments, can alter both the organic matter dynamics and the composition, structure and function of stream macroinvertebrate assemblages. Although it is an issue of great concern elsewhere, in Andean headwater streams scarce information exist about this respect. By using a paired-catchment approach (thinned vs. unthinned) in two sets of selected evergreen and deciduous small streams in southern Chile (39°S), we evaluated the effects of forest harvest on seasonal and annual litterfall dynamics and the structural and functional attributes of macroinvertebrates between January 2008 and January 2009. Metrics used to assess changes included riparian litterfall input, invertebrate colonization and leaf decomposition of dominant plant species (evergreen: Laureliopsis philippiana, Myrceugenia planipes; deciduous: Nothofagus alpina), taxa richness, functional feeding group (FFG) composition, and their densities and biomasses for each stream. In both experimental trials, microcatchments registered significant differences in the seasonal litterfall input. The total organic matter input was as follows: Unthinned evergreen (UE)=3699, thinned evergreen (TE)=3249, unthinned deciduous (UD)=3151, and thinned deciduous (TD)=2981kgha−1y−1. Leaf dry mass losses were significantly higher during summer and spring for L. philippiana and during summer and autumn for N. alpina. These results were concomitant to decomposition rates and macroinvertebrate abundance during colonization of the leaf bags. Macroinvertebrate density and biomass were also contrasted; shredders were the dominant FFG and showed significant seasonal differences between microcatchments in both in-stream and leaf bag studies. There were generally no major changes in FFG composition or taxa richness, but differences were detected comparatively in the abundance or density of collectors and shredders. Our results suggest that forestry activities carried out on riparian vegetation of Andean headwater streams can affect the structural and functional role of plants and benthic invertebrates and nutrient fluxes downstream.

Leaf and root litter decomposition is discontinued at high altitude tropical montane rainforests contributing to carbon sequestration.

We investigated how altitude affects the decomposition of leaf and root litter in the Andean tropical montane rainforest of southern Ecuador, that is, through changes in the litter quality between altitudes or other site‐specific differences in microenvironmental conditions. Leaf litter from three abundant tree species and roots of different diameter from sites at 1,000, 2,000, and 3,000 m were placed in litterbags and incubated for 6, 12, 24, 36, and 48 months. Environmental conditions at the three altitudes and the sampling time were the main factors driving litter decomposition, while origin, and therefore quality of the litter, was of minor importance. At 2,000 and 3,000 m decomposition of litter declined for 12 months reaching a limit value of ~50% of initial and not decomposing further for about 24 months. After 36 months, decomposition commenced at low rates resulting in an average of 37.9% and 44.4% of initial remaining after 48 months. In contrast, at 1,000 m decomposition continued for 48 months until only 10.9% of the initial litter mass remained. Changes in decomposition rates were paralleled by changes in microorganisms with microbial biomass decreasing after 24 months at 2,000 and 3,000 m, while varying little at 1,000 m. The results show that, irrespective of litter origin (1,000, 2,000, 3,000 m) and type (leaves, roots), unfavorable microenvironmental conditions at high altitudes inhibit decomposition processes resulting in the sequestration of carbon in thick organic layers.

Organic matter dynamics in a savanna transition riparian zone: input of plant reproductive parts increases leaf breakdown process

&lt;p&gt;The dynamics of coarse particulate organic matter (CPOM) drives the functioning of most low order freshwater ecosystems. We evaluated plant litter input, litterfall, leaf litter breakdown rates, and the aquatic invertebrate community over the course of one year in a stream situation in a transition zone between savannah and Atlantic forest. Total organic matter input (litter fall) was 335 g m&lt;sup&gt;-2&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;, which was mainly composed of leaves (50%). Higher values are found in the transition from dry to rainy season (September and October), probably in response to water stress. The remaining leaf mass (65% on average) was lowest in May (49%) and highest in August (79%). CPOM productivity in this transition riparian zone is higher than in other savannah systems, but lower than in Atlantic forest. The higher leaf litter breakdown in May was likely accompanied by environmental enrichment due to increase in fruits and flowers (high energy resources). The coefficient of decomposition was classified as fast (k= -0.016) and showed a positive relationship with water flow (increase in physical abrasion). Collected invertebrates were classified as 6% shredders and 12% scrapers. The remaining leaf mass showed a negative relationship with scraper abundance, highlighting the importance of these trophic groups in tropical streams. We can conclude that climate factors (e.g., rainfall) directly affect the input and quality of CPOM and, consequently, leaf decomposition in savanna/Atlantic forest transition zones. &lt;/p&gt;

Enhanced ecosystem functioning following stream restoration: The roles of habitat heterogeneity and invertebrate species traits

Abstract Habitat restoration is increasingly undertaken in degraded streams and rivers to help improve biodiversity and ecosystem functioning. Follow‐up assessments focused on outcomes for biodiversity have often found scant evidence for recovery, raising concerns about the efficacy of habitat restoration for improving ecological integrity. However, responses of other ecological variables, such as ecosystem process rates and the functional trait composition of biological assemblages, have been little evaluated. We assessed how the restoration of habitat heterogeneity affected multiple functional parameters in 20 boreal stream reaches encompassing both more and less extensively restored sites, as well as channelised and natural reference sites. We further assessed relationships between our functional parameters and a fluvial geomorphic measure of habitat heterogeneity. Leaf decomposition was positively related to habitat heterogeneity. This was associated with shifts in the functional composition of detritivore assemblages, with the most obligate litter consumers more prominent in reaches showing higher habitat heterogeneity. The deposition of fine particulate organic matter was consistently higher in restored than channelised sites, and was positively related to the heterogeneity gradient. Algal biomass accrual per unit area did not vary either with restoration or the heterogeneity gradient. Synthesis and applications. Our findings demonstrate that restoration of river habitat heterogeneity can enhance retention and decomposition of organic matter, key ecosystem properties underpinning ecosystem functioning and service delivery. Significantly, enhanced litter decomposition was linked with a change in the functional composition rather than diversity of detritivore assemblages. Future evaluation of the success of habitat restorations should incorporate quantification of ecosystem processes and the functional traits of biota, in addition to measures of fluvial geomorphology and more traditional biotic metrics, to facilitate a more comprehensive and mechanistic assessment of ecological responses.

Succession and Natural Occurrence of Saprobic Fungi on Leaves ofMagnolia liliiferain a Tropical Forest

Leaves of Magnolia liliifera were selected to evaluate fungal diversity, and succession of fungi during leaf decomposition, and the effect of baiting on fungal diversity. The leaf samples were from Doi Suthep-Pui National Park, Chiang Mai, Thailand. Twenty-three taxa were identified on senescent leaves of M. liliifera during the decay process. Distinct fungal communities were observed with the dominant species on the leaves being different at each succession stage. The most abundant fungal species were Hyponectria sp. 1 (on 60% of leaves), Volutella sp. 1 (60%), Gliocladium sp. 3 (37.1%), Corynespora cassiicola (34.3%), Bionectria ochroleuca (25.7%), Cylindrocladium floridanum (22.8%), Phaeosphaeria sp. (17.1%), Dactylaria longidentata (11.4%) and Lasiosphaeria sp. (11.4%). Leaf bait trials did not show any noticeable effect on fungal diversity when either the upper or lower leaf surface was adjacent to the forest floor. Highest fungal diversity on leaves of M. liliifera occurred between day 4 and 40, with most species being present on day 40. On day 56, leaves were found to be skeletonized, and the fungal communities had decreased in number.

Decomposition of terrestrial resource subsidies in headwater streams: Does consumer diversity matter?

AbstractResource subsidies and biodiversity are essential for maintaining community structure and ecosystem functioning, but the relative importance of consumer diversity and resource characteristics to decomposition remains unclear. Forested headwater streams are detritus‐based systems, dependent on leaf litter inputs from adjacent riparian ecosystems, and decomposition of these resources is an important ecosystem function. Here, we examined the effects of consumer community diversity on leaf decomposition in a reciprocal transplant experiment. We asked (1) whether stream consumer communities are adapted to local resources and (2) how functional trait diversity among communities affects the leaf decomposition process. We did not find evidence that communities were adapted to locally derived resource subsidies. Instead, we found that consumer biomass and functional trait diversity as well as resource characteristics were the primary biotic drivers of decomposition. Consumer biomass was stimulated by specific resource subsidies, leading to direct and indirect effects of resource subsidies on ecosystem functioning. Contrary to current theory, we show that decomposition was higher with decreased detritivore functional diversity, suggesting dominant traits encompassing a specific niche increased decomposition. We also show that top‐down, consumer diversity effects can be equal in magnitude to the bottom‐up effects of resource characteristics during the decomposition process. Our research illustrates the importance of considering multiple biotic and abiotic drivers interacting via multiple pathways to affect a crucial ecosystem function.