Decomposition of three halophytes in different habitats of an eastern scheldt salt marsh

Summary A 20.5-month study was undertaken to determine detrital processing of the halophytesSpartina anglica, Elytrigia pungens, andHalimione portulacoides in three different habitats of an estuarine salt marsh in the South-West Netherlands. Decomposition was measured using litter-bags of three different mesh sizes to partition the effects of different faunal groups on decomposition. From April 1980 through October 1981 litter-bags were sampled regulary from a creek, the upper marsh, and from a plant-debris belt on the higher marsh. Dry weights and nutritive values were measured and animals were counted. Mainly rates of loss are reported here. Zonal differences were significant. At first, decomposition in the creek was most rapid. After two months the processes in the creek slowed down because of the trapping of silt by the bags, which probably simulated the natural course of the decomposition process in the water. Decomposition on the marsh followed the most regular pattern, while in the plant-debris belt the pattern was very irregular. Population dynamics of microfaunal organisms supported these findings. In the plant-debris belts loss rates seem to be higher than on the marsh, because of the influence of detritivorous macrofaunal organisms. The loss rates of the three plant species differed significantly.Halimione decomposed fastest, especially in the beginning, and in the plant-debris habitat. On the upper marsh and in the plant-debris belt the loss rates ofSpartina seem to be a little higher than those ofElytrigia.Communication No. 233, Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.     

Inundation,Vegetation, and Sediment Effects on Litter Decomposition in Pacific Coast Tidal Marshes

The cycling and sequestration of carbon are important ecosystem functions of estuarine wetlands that may be affected by climate change. We conducted experiments across a latitudinal and climate gradient of tidal marshes in the northeast Pacific to evaluate the effects of climate- and vegetation-related factors on litter decomposition. We manipulated tidal exposure and litter type in experimental mesocosms at two sites and used variation across marsh landscapes at seven sites to test for relationships between decomposition and marsh elevation, soil temperature, vegetation composition, litter quality, and sediment organic content. A greater than tenfold increase in manipulated tidal inundation resulted in small increases in decomposition of roots and rhizomes of two species, but no significant change in decay rates of shoots of three other species. In contrast, across the latitudinal gradient, decomposition rates of Salicornia pacifica litter were greater in high marsh than in low marsh. Rates were not correlated with sediment temperature or organic content, but were associated with plant assemblage structure including above-ground cover, species composition, and species richness. Decomposition rates also varied by litter type; at two sites in the Pacific Northwest, the grasses Deschampsia cespitosa and Distichlis spicata decomposed more slowly than the forb S. pacifica. Our data suggest that elevation gradients and vegetation structure in tidal marshes both affect rates of litter decay, potentially leading to complex spatial patterns in sediment carbon dynamics. Climate change may thus have direct effects on rates of decomposition through increased inundation from sea-level rise and indirect effects through changing plant community composition.     

Hydrologic control of litter decomposition in seasonally flooded prairie marshes

The effect of seasonal inundation on the decomposition of emergent macrophyte litter (Scolochloa festucacea) was examined under experimental flooding regimes in a northern prairie marsh. Stem and leaf litter was subjected to six aboveground inundation treatments (ranging from never flooded to flooded April through October) and two belowground treatments (nonflooded and flooded April to August). Flooding increased the rate of mass loss from litter aboveground but retarded decay belowground. Aboveground, N concentration decreased and subsequently increased earlier in the longer flooded treatments, indicating that flooding decreased the time that litter remained in the leaching and immobilization phases of decay. Belowground, both flooded and nonflooded litter showed an initial rapid loss of N, but concentration and percent of original N remaining were greater in the nonflooded marsh throughout the first year. This suggested that more N was immobilized on litter under the nonflooded, more oxidizing soil conditions. Both N concentration and percent N remaining of belowground litter were greater in the flooded than the nonflooded marsh the second year, suggesting that N immobilization was enhanced after water-level drawdown. These results suggest different mechanisms by which flooding affects decomposition in different wetland environments. On the soil surface where oxygen is readily available, flooding accelerates decomposition by increasing moisture. Belowground, flooding creates anoxic conditions that slow decay. The typical hydrologic pattern in seasonally flooded prairie marshes of spring flooding followed by water-level drawdown in summer may maximize system decomposition rates by allowing rapid decomposition aboveground in standing water and by annually alleviating soil anoxia.     

Interacting effects of leaf litter species and macrofauna on decomposition in different litter environments

The leaf litter environment (single species versus mixed species), and interactions between litter diversity and macrofauna are thought to be important in influencing decomposition rates. However, the role of soil macrofauna in the breakdown of different species of leaf litter is poorly understood. In this study we examine the multiple biotic controls of decomposition – litter quality, soil macrofauna and litter environment and their interactions. The influence of soil macrofauna and litter environment on the decomposition of six deciduous tree species (Fraxinus excelsior L., Acer pseudoplatanus L., Acer campestre L., Corylus avellana L., Quercus robur L., Fagus sylvatica L.) was investigated in a temperate forest, Wytham Woods, Southern England. We used litterbags that selectively excluded macrofauna to assess the relative importance of macrofauna versus microbial, micro and mesofauna decomposition, and placed single species bags in either conspecific single species or mixed species litter environments. The study was designed to separate plant species composition effects on litter decomposition rates, allowing us to evaluate whether mixed species litter environments affect decomposition rates compared to single species litter environments, and if so whether the effects vary among litter species, over time, and with regard to the presence of soil macrofauna. All species had faster rates of decomposition when macrofauna were present, with 22–41% of the total mass loss attributed to macrofauna. Macrofauna were most important for easily decomposable species as soon as the leaves were placed on the ground, but were most important for recalcitrant species after nine months in the field. The mass loss rates did not differ between mixed and single species litter environments, indicating that observed differences between single species and mixed species litterbags in previous field studies are due to the direct contact of neighbouring species inside the litterbag rather than the litter environment in which they are placed.     

Invasive Grass Alters Litter Decomposition by Influencing Macrodetritivores

The results of nitrogen (N) fertilization experiments have shown inconsistent rates of plant litter decomposition, a phenomenon that may be explained by dispropotionate influence of animal detritivores (macro-detritivores) on litter mass loss versus that of microbial decomposers, whose activity may be dependent on inorganic N. In turn, macrodetritivores may be influenced by plant species composition via their selection of optimal food resources and habitats. In our experiment, fertilizer had no apparent effect on litter decomposition, suggesting that microbial decomposers did not use the additional inorganic N and/or that macrodetritivores had a greater influence on decomposition. Manipulation of macrodetritivores suggested that plant species composition—dominated in this study by Festuca arundinacea, an exotic, invasive grass, and Aster ericoides, a native forb—caused shifts in detrivore communities and/or feeding patterns that tended to increase litter mass loss. Canopy cover of F. arundinacea and A. ericoides ranged from 0% to 11%, suggesting that low-intensity invasion may produce significant changes in ecosystem function, such as decomposition.     

Decomposition in salt marsh ecosystems of the S.W. Netherlands: the effects of biotic and abiotic factors

Decomposition rates, determined with the litterbag technique in salt marshes of the S.W. Netherlands during the past decade are compared; the biotic and abiotic factors influencing these rates are identified and discussed.Tissue composition is the main variable affecting decay rates of halophytes, particularly variations in lignin content between plant parts and between species.Experiments in which the loss of the tensile strength of cotton strips was used as an index of cellulolytic decay, show that there is a conspicuous variation in decay rates on different sites in a salt marsh. Nonetheless, the locally varying environmental conditions within salt marshes of the S.W. Netherlands have less impact on the variation in decomposition rates of halophyte litter than the chemical make-up of the plant material.Larger fauna elements (> 300 m) may increase decomposition rates, but this effect is only limited and depends on location and litter type. The role of small fauna elements such as nematodes, which occur abundantly in association with halophyte litter, remains largely unknown.     

Foliage litter turnover and earthworm populations in three beech forests of contrasting soil and vegetation types

Summary Leaf litter decomposition, levels of accumulated litter as well as the abundance and biomass of earthworms were measured in three mature beech forests in southern Sweden: one mor site, one poor mull site, and one rich mull site. The disappearance rate of beech litter, measured with litter bags, increased with increasing soil fertility. On the rich mull site, the disappearance rate was much higher than in the two other forests, due to the combined effects of higher earthworm activity, more favouable soil moisture conditions, and higher litter quality. Incubating the litter in finely meshed bags (1-mm mesh) to exclude macrofauna had a great effect on litter mass loss in the rich mull site, but it had only a minor effect in the other sites. Simultaneous incubations of local and transplanted leaf litter on the three study sites showed that the substrate quality of the litter increased in the order: mor site — poor mull site — rich mull site. Lignin, N, and P concentrations of the leaf litter failed to explain the observed differences in decomposition rates, and acid/base properties are suggested to be more important. Earthworm numbers per m² were 2.5 (1 species) in the mor, 40 (6 species) in the poor mull and 220 (9 species) in the rich mull forest. Soil chemical conditions, notably pH, were suggested as the main factors determining the inter-site differences in abundance and species composition of earthworms. The role of litter decomposition and earthworm activity in the accumulation of organic matter in the forest floor in different types of beech woodlands are discussed.     

Leaf growth,senescence and decomposition of Juncus maritimus Lam. in a coastal Mediterranean marsh

In this study, the growth, senescence, leaf loss and nutrient dynamics of Juncus maritimus were followed to examine litter decay in a Mediterranean coastal marsh. Decomposition was studied in dead leaves still attached to the plant and in leaves placed in litterbags (detached leaves/litter) on the sediment surface. The dynamics of fungi, meiofauna and epiphytes associated with detached litter were also followed. No significant differences were observed between decay rates in dead leaves attached to plants (0.0017 day⁻¹) and detached leaves (0.0015 day⁻¹) in litter bags. The percentage of ash-free dry weight lost was inversely proportional to the C:N and C:P ratios in plant detritus during decay, indicating N and P limitation for the decomposer community inhabiting decaying J. maritimus litter and uptake of these nutrients from the environment. Water availability and high temperatures on the sediment surface increased the density of meiofauna and epiphyton and decreased fungal biomass during the first 20 days of the experiment. The density of ciliates and nematodes in decomposing litter was inversely related to the C:N ratio and directly related to the percentage of AFDW lost. On the basis of these observations, it was concluded that meiofauna are primary colonizers of J. maritimus leaf litter.     

Microsite and regional variation in the potential decay rate of Sphagnum magellanicum in south Swedish raised bogs

In southern Sweden there are regional gradients in the rate of atmospheric deposition of nitrogen, and the rate of N deposition has increased in recent decades This may have caused a shift in the growth-limiting nutrient of Sphagnum growth from nitrogen to phosphorus In this study, the influence of N and P concentrations on the decay of litter peat formed by Sphagnum magellanicum was examined A total of 90 litter peat samples formed by this species was collected from 15 raised bogs (3 sites per bog, 2 microsites per site) Total N and P of samples were determined and the rate of decomposition (C0₂ release) was measured under aerated, laboratory conditions at 18°C Differences in decomposition rates, N and P concentrations were most pronounced among microsites within sites, whereas no significant differences were observed among bogs The results indicate that decomposition of 5 magellanicum litter peat is influenced more by P than by N Thus, it appears that the recent increase in atmospheric N deposition has not had a large direct effect on peat decomposition rates It is suggested that the efficient uptake of N and P by the Sphagnum plant may lead to a positive feedback mechanism, whereby more slowly growing Sphagnum produces more nutrient-enriched litter peat with a more rapid decay Such a mechanism could promote the development of microtopography (hummocks and hollows) on bogs     

Decomposition processes of Spartina maritima in a salt marsh of the Basque Country

Decomposition dynamics of aerial parts and root-rhizomes of Spartina maritima in a Basque Country salt marsh was studied, using litter bags placed on the soil surface and buried 10 cm below ground. Aerial parts of the plant in aboveground position showed higher breakdown rates than samples placed belowground. There was no significant difference found between aerial parts and root-rhizomes buried. Nitrogen and phosphorus followed different dynamics (seasonal changes and progressive losses) that may be a consequence of distinctive mineralization pathways. The low faunal richness and densities belowground reflect the unfavourable life conditions in such a situation and, to a certain extent, the lower decomposition rates of buried litter. Four mathematical expressions that fit the data are presented and discussed.     

Decomposition of roots of three plant communities in a Dutch salt marsh

Results of the first published study on root decomposition in a West European salt marsh are presented. In situ decomposition of roots of Spartinetum, Puccinellietum and Halimionetum communities were investigated using litter bags. Both the temporal pattern of decomposition and decomposition rate of belowground tissues of the three communities differed during 30 weeks in the marsh; Puccinellietum root litter lost 30–45% ash-free dry weight, Halimionetum root litter 17–26% and Spartinetum root litter 7–17%. Compared to aboveground decomposition in salt marshes these rates are low, however they are in the range of results reported for American and Australian salt marshes. Decomposition rates of root material buried at depths of 10 and 20 cm differed and there was a community × depth interaction. Initial content of structural components was highest in Halimionetum root litter and lowest in Puccinellietum root litter. Integrated soil temperature was highest in the Puccinellietum habitat, while flooding frequency was lowest in the Halimionetum habitat. Results indicate that environmental conditions can cause irregular fluctuations in belowground decomposition rates.     

Leaf growth,senescence and decomposition of Juncus maritimus Lam. in a coastal Mediterranean marsh

In this study, the growth, senescence, leaf loss and nutrient dynamics of Juncus maritimus were followed to examine litter decay in a Mediterranean coastal marsh. Decomposition was studied in dead leaves still attached to the plant and in leaves placed in litterbags (detached leaves/litter) on the sediment surface. The dynamics of fungi, meiofauna and epiphytes associated with detached litter were also followed. No significant differences were observed between decay rates in dead leaves attached to plants (0.0017 day⁻¹) and detached leaves (0.0015 day⁻¹) in litter bags. The percentage of ash-free dry weight lost was inversely proportional to the C:N and C:P ratios in plant detritus during decay, indicating N and P limitation for the decomposer community inhabiting decaying J. maritimus litter and uptake of these nutrients from the environment. Water availability and high temperatures on the sediment surface increased the density of meiofauna and epiphyton and decreased fungal biomass during the first 20 days of the experiment. The density of ciliates and nematodes in decomposing litter was inversely related to the C:N ratio and directly related to the percentage of AFDW lost. On the basis of these observations, it was concluded that meiofauna are primary colonizers of J. maritimus leaf litter.     

Macrofauna assemblage composition and soil moisture interact to affect soil ecosystem functions

Changing climatic conditions and habitat fragmentation are predicted to alter the soil moisture conditions of temperate forests. It is not well understood how the soil macrofauna community will respond to changes in soil moisture, and how changes to species diversity and community composition may affect ecosystem functions, such as litter decomposition and soil fluxes. Moreover, few studies have considered the interactions between the abiotic and biotic factors that regulate soil processes. Here we attempt to disentangle the interactive effects of two of the main factors that regulate soil processes at small scales - moisture and macrofauna assemblage composition. The response of assemblages of three common temperate soil invertebrates (Glomeris marginata Villers, Porcellio scaber Latreille and Philoscia muscorum Scopoli) to two contrasting soil moisture levels was examined in a series of laboratory mesocosm experiments. The contribution of the invertebrates to the leaf litter mass loss of two common temperate tree species of contrasting litter quality (easily decomposing Fraxinus excelsior L. and recalcitrant Quercus robur L.) and to soil CO₂ fluxes were measured. Both moisture conditions and litter type influenced the functioning of the invertebrate assemblages, which was greater in high moisture conditions compared with low moisture conditions and on good quality vs. recalcitrant litter. In high moisture conditions, all macrofauna assemblages functioned at equal rates, whereas in low moisture conditions there were pronounced differences in litter mass loss among the assemblages. This indicates that species identity and assemblage composition are more important when moisture is limited. We suggest that complementarity between macrofauna species may mitigate the reduced functioning of some species, highlighting the importance of maintaining macrofauna species richness.     

Habitat Complexity Enhances Comminution and Decomposition Processes in Urban Ecosystems

Decomposition of organic matter is an essential process regulating fluxes of energy and matter within ecosystems. Although soil microbes drive decomposition, this is often facilitated by detritivores through comminution. The contribution of detritivores and microbes to comminution and decomposition processes is likely to be affected by the habitat complexity. In urban ecosystems, human activities and management of vegetation and litter and soil components determine habitat complexities unobserved in natural ecosystems. Therefore, we investigated the effect of habitat complexity of low- and high-complexity urban parks and high-complexity woodland remnants on microbial decomposition and detritivore comminution using litter bags of differing mesh size. Detritivores were sampled using pitfall traps and their assemblage structure related to rates of comminution. Habitats of lower complexity had significantly lower decomposition and comminution rates. In more complex habitats, site history did not affect decomposition and comminution processes. Vegetation complexity and the indirect effect on microclimate explained most of the variation in decomposition and comminution processes. The abundance of macrofauna detritivores and their species richness were both positively related to higher comminution rates. The volume of understory vegetation was the best predictor for both macrofauna detritivore assemblage structure and comminution and decomposition processes. The study demonstrated that relatively modest changes in habitat complexity associated with different management practices can exert significant effects on the decomposition and comminution processes. The structure of detritivores assemblages was also subjected to modifications of the habitat complexity with significant effects on comminution processes. Simple management practices aimed to increase the complexity of habitats, particularly in the understory vegetation and litter layers, could restore and enhance soil biodiversity and functioning in urban ecosystems.     

闽江河口湿地植物枯落物立枯和倒伏分解主要元素动态

采用分解袋法,对闽江河口湿地2种挺水植物——芦苇(Phragmites australis)和互花米草(Spartina alterniflora)花和叶枯落物的立枯和倒伏分解过程及C、N、P元素动态进行研究。结果表明:(1)立枯分解是2种湿地盐沼植物重要的分解阶段,干物质损失率在13.26%—31.89%之间。多项式模型能较好描述2种植物花和叶的枯落物分解残留率动态。(2)立枯分解阶段,芦苇花和叶的C含量主要为波动下降,互花米草较为稳定;倒伏阶段后期,2种植物都以升高为主。立枯分解阶段2种植物枯落物N含量略有下降,而倒伏阶段逐渐上升。分解过程中枯落物P含量的波动较大。(3)2种植物花和叶C、N的NAI值在分解过程中<100%。芦苇的花和叶中P的NAI值在立枯和倒伏分解阶段都经历了明显下降和升高的过程,而互花米草在立枯阶段变化不大,倒伏阶段下降较为明显。(4)与芦苇相比,互花米草的花和叶枯落物C库较高,N库较低,P库差异不大。     

Chemistry and toughness predict leaf litter decomposition rates over a wide spectrum of functional types and taxa in central Argentina

Litter decomposition, a major determinant of ecosystem functioning, is strongly influenced by the litter quality of different species. We aimed at (1) relating interspecific variation in leaf litter decomposition rate to the functional types different species belong to; and (2) understanding the chemical and/or physical basis for such variation and its robustness to environmental factors. We selected 52 Angiosperms from a climatic gradient in central-western Argentina, representing the widest range of functional types and habitats published so far. Ten litter samples of each species were simultaneously buried for 9 weeks during the 1996 summer in an experimental decomposition bed. Decomposition rate was defined as the percentage of dry mass loss after incubation. Chemical litter quality was measured as carbon (C) content, nitrogen (N) content, and C-to-N ratio. Since tensile strength of litter and living leaves were strongly correlated, the latter was chosen as an indicator of physical litter quality. A subset of 15 species representing different functional types was also incubated in England for 15 weeks, following a similar experimental procedure. Litter C-to-N and leaf tensile strength of the leaves showed the strongest negative associations with decomposition rate, both at the species and at the functional-type level. Decomposition rates of the same species in Argentina and in England were strongly correlated. This reinforces previous evidence that species rankings in terms of litter decomposition rates are robust to methodological and environmental factors. This paper has shown new evidence of plant control over the turnover of organic matter through litter quality, and confirms, over a broad spectrum of functional types, general models of resource allocation. The strong correlations between leaf tensile strength – a trait that is easy and quick to measure in a large number of species – decomposition rate, and C-to-N ratio indicate that leaf tensile strength can be useful in linking plant quality to decomposition patterns at the ecosystem level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydrologic alterations impact plant litter decay rate and ecosystem resilience in Mojave wetlands

Understanding ecosystem processes is vital for effective restoration of degraded ecosystems, especially wetlands. Restoration has become a necessity for management and conservation of the federally endangered Amargosa vole (Microtus californicus scirpensis) endemic to small, bulrush (Schoenoplectus americanus) dominated wetlands in the Mojave Desert. Recent data indicate catastrophic decrease of the vole population and its habitat from local alterations to hydrology, combined with diminished decomposition rates of bulrush, persistence of plant litter, and minimal plant growth except along narrow margins along stream edges. We conducted a series of three field and one greenhouse experiment(s) testing the effect of (1) moisture level on plant decay rate, (2) litter removal on plant regeneration, (3) the interactive effect of litter removal and moisture level increase on plant regeneration, and (4) potential germination rate of bulrush seeds under multiple hydrologic regimes to understand how hydrologic alteration and litter decay ultimately influences marsh regeneration. Results revealed decrease in water level caused a 20‐fold reduction in decomposition rates of a degraded marsh. Litter removal alone and in combination with water table restoration significantly and positively affected bulrush resprouting (p < 0.0001 for both). Seed bank experiments showed high rates of germination in saturated and flooded soil conditions, emphasizing the potential role of seedlings in ecosystem recovery. This study shows how the interaction of hydrologic change and decreased decomposition can shift an ecosystem toward limits of resilience. These results inform restoration strategies in arid‐region wetlands dominated by plants with slow litter decay where strategic litter removal may beneficially increase plant growth.     

鄱阳湖湿地优势植物枯落物的分解速率及碳、氮、磷释放动态特征

植物枯落物分解对生态系统碳通量和养分循环有至关重要的作用,这一过程主要由3个相互作用的因素决定,即化学（枯落物理化特性）、物理（气候和环境）以及生物（参与枯落物分解的微生物和无脊椎动物）因素。在气候和立地环境条件相同的情况下,枯落物质量是制约分解的内在因素。在鄱阳湖湿地开展了野外定位观测实验,采用分解袋技术研究了鄱阳湖湿地优势植物芦苇（Phragmite）、南荻（Triarrhena lutarioriparia）和薹草（Carex.cinerascens Kükenth）枯落物分解速率及碳（C）、氮（N）、磷（P）元素释放动态特的征差异性。结果表明,在0-150 d内三种植物枯落物的干物质分解速率和残留率以及碳相对归还指数（CRRI）、氮相对归还指数（NRRI）、磷相对归还指数（PRRI）差异性都极其显著。在0-150 d内分解速率都是芦苇的最大,薹草的次之,南荻最小。分解进行150 d后,芦苇、南荻和薹草枯落物干物质残留率依次约为56.57%、67.99%和60.88%,CRRI依次约为57.44%、34.58%和41.75%,NRRI依次约为50.71%、-22.66%、和23.18%,PRRI依次约为88.91%、79.27%和85.63%。用Olson负指数衰减模型拟合方程预测芦苇、南荻、薹草枯落物分解完成50%所需的时间大约依次为184 d、249 d和210 d,分解完成95%所需的时间依次为795 d、1078 d和908 d。芦苇和薹草枯落物碳、氮和磷在分解过程中都表现出净释放模式,而南荻枯落物的碳和磷也一直表现为净释放模式,但是氮一直表现为净积累模式。芦苇分解过程中的营养释放作用最强,而南荻群落对氮的吸收和富集效应最强。研究表明植物种类及基质物质量对枯落物分解及其养分释放有很强的调控作用。今后的研究应考虑不同物种枯落物混合时的分解过程以及分解过程中的微生物因素,以便能揭示植物群落物种多样性及微生物活动在湿地生物地球化学循环中的调控作用机制,以期为鄱阳湖湿地碳、氮和磷的生物地球化学循环提供更新的认识,为鄱阳湖湿地的科学管理、保护与恢复提供科学依据。     

Spatial Variability in Decomposition Rates in a Desert Scrub of Northwestern Mexico

The decomposition of leaf litter for five dominant plant species of a desert scrub in Baja California Sur, Mexico was investigated. We designed a factorial decomposition experiment using decomposition bags and the collected leaf-litter from Prosopis articulata, Jatropha cinerea, J. cuneata, Cyrtocarpa edulis, and Fouquieria diguetti. Factors, such as radiation exposure, rainfall, and the size of litter-consuming organisms were considered. The rates of litter decomposition were calculated for these plant species and the environmental conditions by using single exponential models. The initial concentration of nutrients (C, N, P, K, and Ca) and crude-fiber content of the leaf litter were determined. Our results show that the environmental heterogeneity generated by different conditions of radiation exposure and short-term rainfall patterns are the most relevant factors affecting decomposition processes in this Sonoran desert community. A species-specific pattern was observed in decay rates and mass-loss patterns. Decomposition rates varied from 0.0027 to 0.0201 depending on the species and exposure to different ecological conditions. The decay rates were higher under bare-soil conditions and during a wet year than under the shade provided by the canopy of nurse trees and during a dry year. The leaf litter of J. cuneata reincorporated to the soil more rapidly than that of P. articulata and C. edulis. Termites were the more important macroarthropods associated with litter decomposition, and their harvest distribution was independent of the resources distribution. The ecological significance of these results is discussed considering the extreme climatic conditions prevailing in this region.