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Oribatid mite communities and foliar litter decomposition in canopy suspended soils and forest floor habitats of western redcedar forests, Vancouver Island, Canada
Abstract
Litter decomposition and changes in oribatid mite community composition were studied for 2 years in litterbags collected from arboreal organic matter accumulations (canopy suspended soils) and forest floors associated with western redcedar trees on Vancouver Island, British Columbia. We tested the hypotheses that lower rates of mass loss, higher nutrient levels, and different patterns of oribatid mite richness and abundance in decomposing western redcedar litter would be observed in litterbags associated with canopy suspended soils compared to forest floors. Decomposition, measured by mass loss of cedar litter in litterbags, was not significantly different in canopy and forest floor habitats, although reduced in the canopy. Abundance and richness of oribatid mites inhabiting litterbags were significantly greater on the forest floor compared to the canopy suspended soils. Canopy suspended soils had higher levels of total nitrogen, available phosphorus and potassium than the forest floor, but moisture content was significantly lower in the suspended soils. Higher nutrient levels in the canopy system are attributed to differences in coarse woody debris input (but not foliar litter), combined with reduced nutrient uptake by roots and lower mobilisation rates of nutrients by detritivorous and fungivorous microarthropods. Moisture limitation in the canopy system possibly contributed to lower mass loss in litterbags, and lower abundance and richness of oribatid mites in litterbags placed on canopy suspended soils. Patterns of oribatid mite community composition were related to mite communities associated with the underlying substrate (forest floor or canopy suspended soil) which act as source pools for individuals colonising litterbags. Successional and seasonal trends in oribatid mite communities were confounded by moisture limitation at 24 months, particularly within the canopy habitat.
... However, information on decomposition in the canopy is still scarce, and observations are inconsistent. Some studies have found that decay in the canopy is slower than in terrestrial soil when litter is incubated on branches and limb junctions (Nadkarni and Matelson 1991;Clark et al. 1998;Lindo and Winchester 2007;Li et al. 2014), while others report that decomposition can be as fast or even faster than in the pedosphere when this process takes place in the canopy of understory plants or epiphytes such as tank bromeliads (Paoletti et al. 1991;Dearden and Wardle 2008). This discrepancy may be the result of differences in biotic and abiotic conditions occurring at a fine spatial scale. ...
... Canopy decomposition studies are typically not standardized. Although most studies use the litterbag technique, protocols differ substantially in regard to litter type, incubation time, and bag characteristics such as size and mesh opening (Paoletti et al. 1991;Clark et al. 1998;Lindo and Winchester 2007;Dearden and Wardle 2008;Cardelús 2010;Prescott 2010;Li et al. 2014;LeCraw et al. 2017). As a result, studies are only partially comparable as is the identification of common drivers of litter decomposition using such heterogeneous data (Didion et al. 2016;Djukic et al. 2018). ...
... In the five forests, mass loss was slower in the canopy than in the soil only when litterbags were placed on branches (Fig. 3a, b). A slower decomposition rate in the canopy has also been reported for tropical, subtropical and temperate forests, when litter bags were put on branches, trunk reiterations or limb junctions (Nadkarni and Matelson 1991;Lindo and Winchester 2007;Cardelús 2010;Li et al. 2014). The slower decay in these canopy microsites can be explained by their particular microclimatic conditions and interaction with decomposer communities. ...
Plant litter decomposition is a key ecological process that is mostly studied at the forest floor. However, decomposition generally starts in the canopy. In this study, we evaluated the effect of litter composition and climate on the initial phase of decomposition in the soil and two contrasting types of canopy microsites along an elevational gradient (0-2200 m a.s.l.). To this end, we incubated standard material composed by green (fast decomposing) and rooibos (slow decomposing) tea bags for three months. Tea bags were placed in soil (buried at 5 cm) and in the canopy at ca. 5 m above the ground in ''micro-wetlands'' (tank bromeliads) and dry crown microsites (branches). Along the elevational gradient, green tea decomposed faster than rooibos tea in all microsites and forests. Mass loss for both tea types was lowest on branches at all sites, except for green tea in a wet forest where decomposition did not significantly differ among microsites. In wet forests, decomposition did not differ between bromeliads and soil, while in a dry forest, decomposition was faster in bromeliads. We found that the effects of climatic variables [monthly average temperature (TEMP) and total precipitation (PREC) for the incubation months] on decomposition differed between microsites. Along the elevational gradient, the mass loss in soil was positively correlated with TEMP but not with PREC, whereas on branches, mass loss was negatively correlated with TEMP and positively correlated with PREC. Unlike on branches, mass loss in bromeliads slightly decreased with PREC and increased with TEMP. Our study shows that microsite conditions interact with climate (TEMP and PREC) leading to differences in the general decomposition patterns in the forest canopy.
... However, information on decomposition in the canopy is still scarce, and observations are inconsistent. Some studies have found that decay in the canopy is slower than in terrestrial soil when litter is incubated on branches and limb junctions (Nadkarni and Matelson 1991;Clark et al. 1998;Lindo and Winchester 2007;Li et al. 2014), while others report that decomposition can be as fast or even faster than in the pedosphere when this process takes place in the canopy of understory plants or epiphytes such as tank bromeliads (Paoletti et al. 1991;Dearden and Wardle 2008). This discrepancy may be the result of differences in biotic and abiotic conditions occurring at a fine spatial scale. ...
... Canopy decomposition studies are typically not standardized. Although most studies use the litterbag technique, protocols differ substantially in regard to litter type, incubation time, and bag characteristics such as size and mesh opening (Paoletti et al. 1991;Clark et al. 1998;Lindo and Winchester 2007;Dearden and Wardle 2008;Cardelús 2010;Prescott 2010;Li et al. 2014;LeCraw et al. 2017). As a result, studies are only partially comparable as is the identification of common drivers of litter decomposition using such heterogeneous data (Didion et al. 2016;Djukic et al. 2018). ...
... In the five forests, mass loss was slower in the canopy than in the soil only when litterbags were placed on branches (Fig. 3a, b). A slower decomposition rate in the canopy has also been reported for tropical, subtropical and temperate forests, when litter bags were put on branches, trunk reiterations or limb junctions (Nadkarni and Matelson 1991;Lindo and Winchester 2007;Cardelús 2010;Li et al. 2014). The slower decay in these canopy microsites can be explained by their particular microclimatic conditions and interaction with decomposer communities. ...
Plant litter decomposition is a key ecological process that is mostly studied at the forest floor. However, decomposition generally starts in the canopy. In this study, we evaluated the effect of litter composition and climate on the initial phase of decomposition in the soil and two contrasting types of canopy microsites along an elevational gradient (0-2200 m a.s.l.). To this end, we incubated standard material composed by green (fast decomposing) and rooibos (slow decomposing) tea bags for three months. Tea bags were placed in soil (buried at 5 cm) and in the canopy at ca. 5 m above the ground in ''micro-wetlands'' (tank bromeliads) and dry crown microsites (branches). Along the elevational gradient, green tea decomposed faster than rooibos tea in all microsites and forests. Mass loss for both tea types was lowest on branches at all sites, except for green tea in a wet forest where decomposition did not significantly differ among microsites. In wet forests, decomposition did not differ between bromeliads and soil, while in a dry forest, decomposition was faster in bromeliads. We found that the effects of climatic variables [monthly average temperature (TEMP) and total precipitation (PREC) for the incubation months] on decomposition differed between microsites. Along the elevational gradient, the mass loss in soil was positively correlated with TEMP but not with PREC, whereas on branches, mass loss was negatively correlated with TEMP and positively correlated with PREC. Unlike on branches, mass loss in bromeliads slightly decreased with PREC and increased with TEMP. Our study shows that microsite conditions interact with climate (TEMP and PREC) leading to differences in the general decomposition patterns in the forest canopy.
... It has been known for a long time that Oribatida also occur on trees [9], and researchers soon recognized that species composition differs between soil and tree canopy [10,11]. Since then, many eco-faunistic studies targeted the diversity of oribatids on trees [12][13][14][15]. However, many previous studies provided often confusing, disparate information on individual species or species communities inhabiting trees, which indicates that abundance, distribution and diversity of tree-living species vary considerably even under presumably similar conditions. ...
... As in [21], however, we can conclude that life on tree already evolved within the Crotonioidea. In this context it is also interesting to note that representatives of Enarthronota and Mixonomata, Liochthonius sp., and Epilohmannia sp. have been collected from suspended soil samples in North America [15,46], and Liochthonius pseudolaticeps has been found on bark of trees in Spain [47]. This suggests that the preconditions for colonizing tree trunks and canopies were already present in the early-derived oribatids, indicating a repeated independent evolution of tree life. ...
... Many taxa included in our study are known to occur both in soil and on trees, e.g., [15]; only 14 of the 165 included species are almost exclusively tree-living. The occurrence of soil-dwelling oribatids on trees might be explained for example by so called suspended soils on trees, which provide ecological conditions similar to the forest floor [15]. ...
Though mostly soil dwelling, oribatid mites are found in all kind of habitats, with several species exclusively living on trees. Using previously published DNA sequences and eco-morphological data available from the literature, we inferred the number of transitions between soil dwelling to a truly arboreal lifestyle in oribatid mites and the shape evolution of a particular morphological structure of a sense organ (bothridial seta (= sensillus) of a trichobothrium), the shape of which was previously reported to be associated with an arboreal lifestyle. Our data suggest that a truly arboreal lifestyle evolved several times independently in oribatid mites, but much less often than previously proposed in the past. Even though all truly arboreal species indeed seem to possess a capitate sensillus, this character is not exclusive for arboreal taxa. Nonetheless, since all truly arboreal species do have a capitate sensillus, this might be considered an important (pre-)adaptation to a life on trees. We further provide guidelines on how the term “arboreal” should be applied in future mite research and emphasize the importance of exact microhabitat characterization, as this will greatly facilitate comparisons across studies.
... However, if this sequence is not followed, organic matter does not enter the litter at the same time, but rather it accumulates on the surface of the forest obstacles. Such soils can exist for a long time in the form of undecomposed organic matter that is stabilized by various kinds of epiphytes, and the rate of organic matter decomposition in the canopy compared with that in the litter may change over time [13]. ese soils are formed in places such as cracks, on branches, in tree bark, and in epiphytic associations, and they temporarily delay the organic matter from getting onto the surface of the soil [14]. ...
... It was shown previously that suspended soils contain a higher content of total nitrogen, phosphorus, and potassium and have a signi cantly lower moisture content compared with the forest soil. Higher levels of nutrients in the canopy system are explained by di erences in the intake of coarsegrained wood waste (but not foliar litter) combined with a decrease in nutrient uptake by roots and less mobilization of nutrients by detritus and fungi [13]. e limited amount of humidity in the canopy system may have contributed to a reduction in weight loss, as well as a lower abundance and richness of oribatide mites, in garbage bags placed on the suspended soil under the canopy. ...
... 13 C-NMR spectras of humic acids, extracted from suspended (a) and phorophyte (b and c) soils. ...
Humification is considered to be a global process that is implemented in soils and organic sediments and also in natural water and air. The term “suspended soils” has become increasingly common in recent years. Suspended soils are defined as the part of the organic matter that has not undergone the full decomposition process and has not turned into the humus of terrestrial soils. Suspended soils were shown to contain higher total nitrogen, phosphorus, and potassium contents than the forest soil, but the moisture content in suspended soils was significantly lower. Our study of the structural composition of humic substances in suspended soils was conducted with an aim of evaluating the humification rates and structural composition of humic acids in the suspended soil in tropical forests of South Vietnam. Soil samples from three selected areas were investigated: the soil under phorophytes (mineral soil presented by samples of topsoil of the typical dry savanna landscape) and two soils from epiphytous formations. Samples were collected from savanna-type sparse communities, located on oligotrophous plains in Phú Quốc Island (South Vietnam) in 2015. General properties of the soil and the elemental composition of suspended soils were determined, and the humic substance chemical composition was evaluated using solid state ¹³ C-NMR. Data obtained showed that the pH of the soils under phorophytes was higher than in the suspended soils; basal respiration did not tend to change indices between soils under phorophytes and suspended soils, but the suspended soil was less enriched by nitrogen than the soil under phorophytes. This can be related to the total amount of organic matter exposed to humification in various soils and to the presence of an essential portion of mineral particles in the soil under phorophytes. Data on elemental composition of the humic acids (HAs) indicated that one method of humification is implemented in all three soils that were investigated. The humic acids of the phorophyte soil showed the same content of aromatic fraction as the suspended soil. The most comparable soil type in terms of humic substance composition is Cambisols from humid forests of subboreal and subtropical zones. The humification process implemented in suspended soils showed the absence of mineral compounds or mineral fine earth, which indicated that humification in conditions of pure organic substrates can result in formation of deep humified organic matter, as shown by humic acids with an essential aromatic fraction content.
... Arthropods have important functional roles in old-growth forests, as well as in other ecosystems [9,68,[79][80][81]. Arthropods are primary factors affecting turnover of plant material, nutrients, and water. ...
... Arthropods are primary factors affecting turnover of plant material, nutrients, and water. Herbivore tissues, feces, green foliage fragments, and throughfall (precipitation percolating through the forest canopy) provide more consistent supply of nutrients to the forest floor community, for eventual uptake by plants, than would occur in their absence [9,[79][80][81]. Detritivores initiate the process of decomposition by fragmenting and inoculating detritus with saprophagous microorganisms [9,15] and are instrumental in the return of nutrients to soil for uptake by plants and production of new plant tissues [9,15,81]. ...
... Herbivore tissues, feces, green foliage fragments, and throughfall (precipitation percolating through the forest canopy) provide more consistent supply of nutrients to the forest floor community, for eventual uptake by plants, than would occur in their absence [9,[79][80][81]. Detritivores initiate the process of decomposition by fragmenting and inoculating detritus with saprophagous microorganisms [9,15] and are instrumental in the return of nutrients to soil for uptake by plants and production of new plant tissues [9,15,81]. Decomposition is delayed in the absence of arthropod detritivores and fungivores [9,61,68]. These processes are critical to sustained primary production [36], although fertilization could accomplish this goal at great expense. ...
Old-growth forests have become rare in North America but provide habitat for unique assemblages of species that often are rare in younger forests. Insects and related arthropods reach their highest diversity in old-growth forests because of their stable moderate temperature and relative humidity and the rich variety of resources represented by high plant species richness and structural complexity. Old-growth arthropod assemblages typically are distinct from those in younger, managed forests. Major subcommunities include the arboreal community that is composed of a rich assemblage of herbivores, fungivores, and their associated predators and parasitoids that function to regulate primary production and nutrient fluxes, the stem zone community that includes bark- and wood-boring species and their associated predators and parasitoids that initiate the decomposition of coarse woody debris, and the forest floor community composed of a variety of detritivores, fungivores, burrowers, and their associated predators and parasitoids that are instrumental in litter decomposition. Insect outbreaks are relatively rare in old-growth forests, where the diversity of resources and predators limit population growth. In turn, insects contribute to plant diversity and limit primary production of host plant species, thereby promoting development of old-growth forest characteristics. Arthropods also provide important functions in decomposition and nutrient cycling that may be lost in younger, managed forests with limited provision of coarse woody debris and accumulated litter. Protection of remnant old-growth forests within the forest matrix may be particularly valuable for maintaining the diversity of plant and arthropod predators that can minimize outbreaks, thereby contributing to resilience to changing environmental conditions.
... Differences in the moisture content of canopy soils can be related to the content of fibrous material. The high concentration of fibers makes canopy soils more susceptible to rapid desiccation than their terrestrial counterparts (Bohlman et al., 1995;Enloe et al., 2006;Lindo and Winchester, 2007). Elevated fiber content also affects the bulk density of canopy soils, which can range between 0.02 and 0.3 g cm −3 (Perez et al., 2005;Enloe et al., 2006). ...
... Base saturation particularly could be influenced by the high Ca content of maple foliar litter (Chandler et al., 2008) that accumulates in the canopy mats. Such inputs are absent in spruce canopy soils, although calcareous material from mollusks and insects could be enhancing the Ca levels of spruce soils (Lowman and Rinker, 2004;Lindo and Winchester, 2007). The lower CEC and base saturation of the spruce canopy soils might limit nutrient availability for epiphytic plants growing on spruce trees compared with epiphytes growing on maple canopy soils. ...
... Furthermore, the higher C/N ratio of the forest floor could be influenced by the woody biomass accumulated on the ground. Woody debris has a higher C/N ratio than foliage litter, and this woody material is less likely to accumulate in the canopy than in the forest floor (Lindo and Winchester, 2007;Berg and McClaugherty, 2008). In temperate forests, the N concentration of canopy soils ranges between 10 and 17 g kg −1 , with C/N ratios ranging between 31 and 41 (Perez et al., 2005;Enloe et al., 2006;Lindo and Winchester, 2007). ...
Canopy or arboreal soils develop from the accumulation and decomposition of epiphytes on branches and in bifurcations of trees in tropical and temperate rainforests. Canopy soils are important because they provide habitat and water, and accumulate allochthonous nutrients for epiphytes and their associated biota. This study characterized the chemical and physical characteristics of canopy soils developed on Sitka spruce [Picea sitchensis (Bong.) Carrière] and bigleaf maple (Acer macrophyllum Pursh) in an old-growth forest at the Queets River watershed, Washington. Bigleaf maple canopy soils were dominated by hemic horizons, had higher pH, N content, cation exchange capacity, and extractable N levels relative to Sitka spruce canopy soils, which had higher bulk density and C/N ratios. Compared with the forest floor, canopy soils had lower total C, total N, and C/N ratio. The bigleaf maple canopy soil was classified as a Typic Haplohemist, whereas the Sitka spruce canopy soil was classified as a Typic Haplosaprist. The main differences between these canopy soils are due to different inputs of host tree litter and decomposition states of the two species. Canopy soils in this ecosystem are enhancing the pool of C and N by 20 and 25%, respectively, relative to the C and N pools of the forest floor. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved.
... Nevertheless, the underlying questions guiding these studies vary considerably, including the collecting techniques, the level of taxonomic identification, and the core group of insects considered. Some studies approach an array of arthropod groups [29][30][31][32][33][34][35][36] , while most focus on particular groups of lepidopterans [37][38][39][40][41][42][43][44][45][46][47] , beetles [48][49][50][51][52][53] , hymenopterans 54-58 , orthopterans 59 , collembolans 60,61 , psocopterans 62 or hemipterans 63 . ...
... Objective two-variability of Diptera at distinct heights of the tropical forest canopy gradient. The (37), Stratiomyidae (32), and Chloropidae (29). We compiled the cases in which the biology of the larvae or of the adult of the genera sampled was known, providing a sketch of the vertical distribution of guilds of flies (Supplementary Information Table S4). ...
Tropical forests are among the most biodiverse biomes on the planet. Nevertheless, quantifying the abundance and species richness within megadiverse groups is a significant challenge. We designed a study to address this challenge by documenting the variability of the insect fauna across a vertical canopy gradient in a Central Amazonian tropical forest. Insects were sampled over two weeks using 6-m Gressitt-style Malaise traps set at five heights (0 m–32 m–8 m intervals) on a metal tower in a tropical forest north of Manaus, Brazil. The traps contained 37,778 specimens of 18 orders of insects. Using simulation approaches and nonparametric analyses, we interpreted the abundance and richness of insects along this gradient. Diptera, Hymenoptera, and Coleoptera had their greatest abundance at the ground level, whereas Lepidoptera and Hemiptera were more abundant in the upper levels of the canopy. We identified species of 38 of the 56 families of Diptera, finding that 527 out of 856 species (61.6%) were not sampled at the ground level. Mycetophilidae, Tipulidae, and Phoridae were significantly more diverse and/or abundant at the ground level, while Tachinidae, Dolichopodidae, and Lauxaniidae were more diverse or abundant at upper levels. Our study suggests the need for a careful discussion of strategies of tropical forest conservation based on a much more complete understanding of the three-dimensional distribution of its insect diversity.
... Such soils can exist for a long time in the form of undercomposed or slightly decomposed organic matter; stabilized by various types of epiphytes (this stabilization could be physical of chemical, depending on the degree of organic matter transformation and the presence and spatial density of living organic tissues in epiphytic suspended formations). Suspended soils in the forest canopy experience large differences in temperature and humidity than in the normal forest litter, located of the mineral or organo mineral soil surface (Bohlman et al. 1995), and the decomposition rate of organic matter in the canopy may be different (Lindo and Winchester 2007). Thus, the slower decomposition of organic matter under the conditions of "air soils" or suspended soil-like formations was revealed in comparison with experimentally designed soils in experiment of the decomposition of cellulose patches in soils (Nadkarni 1986). ...
... Soil fauna is present in suspended soils, for example, mites (Lindo and Winchester 2007) and springtails (Shaw 2015). The process of settling the tree crowns of nonflying fauna is poorly understood, but presumably involves migration along the bark of the tree (Shaw 2015) or transfer on the mineral particles surface by wind. ...
The book represents a collection of papers presented at VI International Symposium "Biogenic - abiogenic interactions in natural and anthropogenic systems" that was held on 24-27 September 2018 in Saint Petersburg (Russia). Papers in this book cover a wide range of topics connecting with interactions between biogenic and abiogenic components in lithosphere, biosphere and technosphere. The main regarding topics are following: methods for studying the interactions between biogenic and abiogenic components; geochemistry of biogenic-abiogenic systems; biomineralization and nature-like materials and technologies; medical geology; biomineralogy and organic mineralogy; biomineral interactions in soil; biodeterioration of natural and artificial materials; biomineral interactions in extreme environment.
... Such soils can exist for a long time in the form of undercomposed or slightly decomposed organic matter; stabilized by various types of epiphytes (this stabilization could be physical of chemical, depending on the degree of organic matter transformation and the presence and spatial density of living organic tissues in epiphytic suspended formations). Suspended soils in the forest canopy experience large differences in temperature and humidity than in the normal forest litter, located of the mineral or organo mineral soil surface (Bohlman et al. 1995), and the decomposition rate of organic matter in the canopy may be different (Lindo and Winchester 2007). Thus, the slower decomposition of organic matter under the conditions of "air soils" or suspended soil-like formations was revealed in comparison with experimentally designed soils in experiment of the decomposition of cellulose patches in soils (Nadkarni 1986). ...
... Soil fauna is present in suspended soils, for example, mites (Lindo and Winchester 2007) and springtails (Shaw 2015). The process of settling the tree crowns of nonflying fauna is poorly understood, but presumably involves migration along the bark of the tree (Shaw 2015) or transfer on the mineral particles surface by wind. ...
There are a number of ways to implementation the epiphytic biogenic-abiogenic interaction in plant communities. Epiphytic plants form a special type of organic or organo-mineral substrate—suspended soils. This study is devoted to the investigation of the biogenic-abiogenic interactions in epiphytic formations and characteristic of the suspended soils, which are formed in them with special reference to the assessment of stabilization rates and structural composition of humic acids in the suspended soil in tropical forests of South Vietnam. General properties of the soil and the elemental composition of suspended soils were determined, and the humic substance chemical composition was evaluated using solid state 13C-NMR. The soils formed by epiphytes show a positive correlation in the isotopic composition of nitrogen with epiphyte tissues and to a greater extent with forophyte tissues and, probably, take part in their nitrogen nutrition, concentrating zoogenic nitrogen due to ant presence. The most comparable soil type in terms of organic matter composition is Cambisols from humid forests of subboreal and subtropical zones. The results we obtained are consistent with the concept of soil organic matter stabilization: the proportion of aliphatic compounds in the component composition in bulk organic matter is higher than in humic acids, isolated from soils investigated. Thus, it can be concluded that in suspended soils soil organic matter stabilization processes active and expressed in formation and accumulation of humic substances.
... Такие почвы могут долгое время существовать в форме неразложившегося органического вещества, стабилизированного различными видами эпифитов. Подвешенные почвы в лесном пологе испытывают большие перепады температур и влажности, чем в лесной подстилке (Bohlman et al., 1995), и скорость разложения органического вещества в пологе по сравнению с подстилкой может быть иной (Lindo, Winchester, 2007). Так, по анализу разложения целлюлозных дисков экспериментально был показан более медленный распад органического вещества в условиях "воздушных почв", чем на земле (Nadkarni, 1986). ...
... Так, по анализу разложения целлюлозных дисков экспериментально был показан более медленный распад органического вещества в условиях "воздушных почв", чем на земле (Nadkarni, 1986). В подвешенных почвах присутствует и почвенная фауна, например клещи (Lindo, Winchester, 2007) и ногохвостки (Shaw, 2015). Процесс заселения кроны деревьев не летающей фауной изучен плохо, но предположительно включает в себя миграцию по коре дерева (Shaw, 2015). ...
Существует ряд путей реализации эпифитного образа жизни у растений. Часть из них связана с ксероморфозом осевых органов, часть – с созданием в кронах более привычных для растений условий. В последнем случае эпифиты путем различных морфологических приспособлений удерживают вокруг себя воду и субстрат, улучшающий их минеральное питание. Исследова¬ли одно из таких адаптивных приспособлений: агеотропные воздушные корни-“улавливатели”. Показали, что эти корни в ряде случаев лишены меристемы, обладая ярко выраженным детер¬минированным ростом, кроме того, обладают особой механической прочностью, за счет видо¬изменения клеток стели. Исследовали также растения, обладающие корнями-“улавливателя¬ми” (“гнездовые” эпифиты) в природе, и близкие к ним по биоморфологии эпифиты. Все они образуют особый тип органического или органоминерального субстрата – подвешенные почвы. Формируемые эпифитами почвы показывают положительную корреляцию в изотопном соста¬ве азота с тканями эпифита и в большей степени с тканями форофита и, вероятно, принимают участие в их азотном питании, концентрируя зоогенный азот благодаря поселению муравьев. Показано, что анатомия и характер роста агеотропных воздушных корней являются примером адаптивной эволюции, благодаря которой растительный организм в ходе онтогенеза формиру¬ет среду, облегчающую его существование в кронах деревьев.
... Our results show that cushions act as habitat patches that support abundant and species-rich communities; the effect is especially pronounced for Oribatida. The impor-tance of disturbance as a structuring force for microarthropod communities, especially for Oribatida, has been stressed frequently (Behan-Pelletier, 1999;Maraun and Scheu, 2000;Lindo and Winchester, 2007). Compared with other microarthropods, oribatid mites are characterized by long life cycles, high adult survival, and low fecundity (Norton, 1994). ...
... Compared with other microarthropods, oribatid mites are characterized by long life cycles, high adult survival, and low fecundity (Norton, 1994). Stability and structural complexity of the habitat are the major determinants of Oribatida species richness (Lindo and Winchester, 2007). While most studies on facilitation of arthropods by cushion plants focus on favorably modified microclimate (see review in Liczner and Lortie, 2014), we suggest that in a patterned ground landscape cushion plants play a critically important role in providing physically stable habitat in a highly disturbed environment. ...
Cushion plants in alpine ecosystems act as nurse species, which modify and alleviate
environmental conditions and positively influence the diversity and abundance of other
organisms. Soil fauna in alpine environments should benefit from nurse plant facilitation,
but this has not been investigated. We compared diversity, abundance, and community
structure of soil microarthropods (Collembola, Oribatida, Mesostigmata, Prostigmata,
Endeostigmata, and Astigmata) under cushion plants and in adjacent open microsites in
high altitude patterned ground landscapes in New Zealand. We investigated how cush-
ion plants influence environmental factors, and how environmental factors and species
traits contribute to microarthropod community structure. The results show that cushion
plants are a key in maintaining the biodiversity of soil microarthropods in the high al-
pine. Cushion plants maintain higher moisture and organic matter content in the soil,
provide productive and structurally complex habitat, and mitigate disturbance. Abun-
dance and species richness of Oribatida, Mesostigmata, and Prostigmata were higher
under cushion plants. In contrast, abundance of Collembola was higher in open micro-
sites, while their species richness similar in and out of cushions. Oribatida assemblages
were dominated by small asexual species, indicating a disturbed environment. Oribatida
community structure was significantly related to the microhabitat in two out of three
mountain ranges. Collembola assemblages were similar in and out of cushions. Higher
soil moisture and organic matter content under cushion plants were significant in ex-
plaining patterns in microarthropod assemblages, although high percentage of variability
was not explained by environmental variables. There was no effect of cushions on soil
temperatures. Species identity of the cushion plant did not influence abundance, species
richness, or community assemblages of mites and springtails; however, some species were
associated with either Dracophyllum or Raoulia cushions.
... In a study conducted in A. macrophyllum canopies along the Queets River, located on the Olympic Peninsula, Haristoy et al. (2014) reported a C/N ratio of 22 for canopy soils, and NH 4 + to be the dominant form of extractable N. This suggests that A. macrophyllum canopy soils have a higher potential for mineralization and thus increased N availability for plants, host tree adventitious roots, and microorganisms (Nadkarni 1994;Brady and Weil 2000;Lindo and Winchester 2007;Berg and McClaugherty 2008). Another potential pathway for fixed N from canopy bryophytes is being deposited to the forest floor as epiphytic litterfall and throughfall. ...
Purpose
Old-growth forests in the Pacific Northwest host a variety of epiphytes on their branches and stem. Given the common and often large epiphytic biomass associated with Acer macrophyllum (Pursh) in this region, we evaluated how seasonal weather changes and urbanization (metal and nitrogen deposition), affect canopy epiphytic N2 fixation in the Hoh Rainforest of the Olympic Peninsula and in urban parks and forests in Seattle.
Methods
We collected Isothecium stoloniferum (Brid.) samples from both the Hoh Rainforest and Seattle at four periods from April 2016 through January 2017. Moss-associated N2 fixation rates were measured in the laboratory using the acetylene reduction assay and trace metal concentrations in the moss were analyzed using NO3 + H2O2 digestion.
Results
We found levels of N2 fixation were highest during the spring sampling period. Elevated levels of heavy metals were observed in I. stoloniferum samples collected in the urban canopies in Seattle where N2 fixation rates were low, suggesting N2 fixation is sensitive to the bioaccumulation of heavy metals. In A. macrophyllum canopies, I. stoloniferum was found to yield 0.1130 g N m⁻² yr⁻¹ in canopy branches within the Hoh Rainforest and only 0.0009 g N m⁻² yr⁻¹ on branches in Seattle.
Conclusions
These results highlight a rarely explored source of biological N2-fixation in temperate rainforests and suggest that epiphytic N2-fixation may contribute bio-available nitrogen in A. macrophyllum stands. N2-fixation in canopy bryophytes was found to be highly sensitive to urban pollution, possibly due to bioaccumulation of heavy metals in bryophyte tissue.
... Detritivorous species are also correspondingly numerous, but most are relatively inconspicuous. Many species in groups such as the Collembola, Isopoda and arachnids like the Orabitida, roam the forest floor and forest canopy, feeding on accumulations of decaying and dead organic and fungal material (Lindo and Winchester, 2007;Paoletti and Hassall, 1999;Lawrence and Wise, 2000;Schneider et al., 2005). Orabitid mites in particular, might reach densities of close to half a million individuals/m 2 in some temperate soil habitats (Schneider et al., 2005). ...
... Each material deposits microbiome will differ from terrestrial soils (Eskov et al. 2021). Material deposits have unique microbial biodiversity (Zytynska et al. 2011) than tropical terrestrial soils (Lindo and Winchester 2007). The presence of flora and fauna in the microhabitat contributes to AGE biodiversity in oil palm plantations (Ganser et al. 2017). ...
Pradiko I, Farrasati R, Rahutomo S, Sapalina F, Pane RDP, Hidayat F, Ginting EN. 2022. The physical, chemical, and biological characteristics of microhabitats inside oil palm trunk axils in North Sumatra, Indonesia. Biodiversitas 23: 3793-3807. Above-ground ecosystems (AGE) components in oil palm plantations consist of epiphytic plants and fauna in microhabitat within the axil of pruned fronds. This research aimed to identify the characteristics of microhabitat, including microclimate profile, physical and chemical properties of the material deposit, epiphyte abundance, and microbe population. The study sites were located in the eastern and western regions of North Sumatra. Furthermore, vertical observations were taken on oil palm trunks at the height of 20, 100, 150, 200, and 300 cm. The study indicated that the microclimate, nutrients content, physical properties of the material deposit, and bacterial populations in the trunk axils of oil palm in the eastern differed from the western region. There was no obvious pattern in the microclimate profile for individual oil palms. However, there was a change in N, C-organic, and C/N ratios with the increasing height of microhabitat sites. In terms of abundance, Nephrolepis bisserata and Vittaria ensiformis epiphytes were more dominant in the upper and bottom trunk, respectively. The microhabitat at the bottom trunk had a denser bacterial population, negatively correlated with N, C-organic, C/N ratio, Mg, and pH.
... Thus, analysis of the decomposition of cellulose discs experimentally showed a slower decomposition of organic matter under conditions of "air soils" than on the ground (Nadkarni, 1986). Suspended soils also contain soil fauna, such as mites (Lindo and Winchester, 2007) and springtails (Shaw, 2015). The process of the colonization of tree crowns by nonflying fauna is poorly understood, but it presumably involves migration along the tree bark (Shaw, 2015). ...
... absence of the small taxa, such the Brachychthoniidae, may reflect either their biology or their microhabitat preferences. Members of this family were found by Lindo and Winchester (2007) in litterbags placed in aerial soils but such aerial soils were absent from our sites. There may thus be microhabitat and behavioural components that contribute to the differences. ...
... We note that our litterbags were placed in the centre of the bryosphere profile, and that even stronger bryosphere effects are likely to occur in the lower parts of the bryosphere (De Long and others 2016). Increased temperature and moisture in the bryosphere may be important in promoting the decomposer subsystem (Lindo and Winchester 2007;Makkonen and others 2012). Although we did not measure moisture content, our finding of higher mean temperatures in summer and autumn in the bryosphere compared to bare ground indicates that improved micro-climate in the bryosphere could have enhanced soil biota activity and thus decomposition. ...
The bryosphere (that is, ground mosses and their associated biota) is a key driver of nutrient and carbon dynamics in many terrestrial ecosystems, in part because it regulates litter decomposition. However, we have a poor understanding of how litter decomposition responds to changes in the bryosphere, including changes in bryosphere cover, moss species, and bryosphere-associated biota. Specifically, the contribution of micro-arthropods to litter decomposition in the bryosphere is unclear. Here, we used a 16-month litterbag field experiment in two boreal forests to investigate bryosphere effects on litter decomposition rates among two moss species ( Pleurozium schreberi and Hylocomium splendens ), and two litter types (higher-quality Betula pendula litter and lower-quality P. schreberi litter). Additionally, we counted all micro-arthropods in the litterbags and identified them to functional groups. We found that bryosphere removal reduced litter decomposition rates by 28% and micro-arthropod abundance by 29% and led to a colder micro-climate. Litter decomposition rates and micro-arthropod abundance were uncorrelated overall, but were positively correlated in B. pendula litterbags. Bryosphere effects on litter decomposition rates were consistent across moss species, litter types, and micro-arthropod abundances and community compositions. These findings suggest that micro-arthropods play a minor role in litter decomposition in the boreal forest floor, suggesting that other factors (for example, micro-climate, nutrient availability) likely drive the positive effect of the bryosphere on decomposition rates. Our results point to a substantial and consistent impairment of litter decomposition in response to loss of moss cover, which could have important implications for nutrient and carbon cycling in moss-dominated ecosystems.
... absence of the small taxa, such the Brachychthoniidae, may reflect either their biology or their microhabitat preferences. Members of this family were found by Lindo and Winchester (2007) in litterbags placed in aerial soils but such aerial soils were absent from our sites. There may thus be microhabitat and behavioural components that contribute to the differences. ...
Arthropods are the most species-rich group in arboreal communities where mites are often both abundant and diverse. Manual sampling by climbers is generally used in studies of arboreal mites but chemical fogging is sometimes used as an alternative sampling method. In this study, mites (Acari: Oribatida, Acari: Mesostigmata) from the canopies of oak, ash, Scots pine and Sitka spruce forests in Ireland were sampled using chemical fogging and climbers. Results show that the inter-tree species comparisons of relative abundances, richness and species composition are very dependent on the method used. The number of taxa collected varied significantly between forest types but the differences varied depending on the method used. The highest species richness was recovered from oak by both techniques but the fogging samples suggested that Scots pine forests were the least diverse while manual collection suggested Sitka spruce were the least diverse. Each technique preferentially recovered different components of the assemblages. Fogging was the more efficient method for collecting large active species while climbers were the most effective way to sample small species inhabiting epiphytes. Neither method is more effective than the other, and both should instead be viewed as complementary. The use of both methods would provide a more comprehensive view of the canopy mite fauna.
... Так, по ана-ЖУРНАЛ ОБЩЕЙ БИОЛОГИИ том 82 № 5 2021 ЕСЬКОВ, КОЛОМЕЙЦЕВА лизу разложения целлюлозных дисков экспериментально был показан более медленный распад органического вещества в условиях "воздушных почв", чем на земле (Nadkarni, 1986). В подвешенных почвах присутствует и почвенная фауна, например, клещи (Lindo, Winchester, 2007) и ногохвостки (Shaw, 2015). Процесс заселения кроны деревьев нелетающей фауной изучен плохо, но предположительно включает в себя миграцию по коре дерева (Shaw, 2015). ...
В обзоре, первом на русском языке, затронуты вопросы экологического и ботанического феномена
эпифитизма сосудистых растений. Обсуждается проблема происхождения эпифитизма, его экологических границ и современного понимания экоморфологических особенностей эпифитов. Рассмотрены различные подходы к классификации эпифитов, включая авторские, обсуждается соотношение
современной англоязычной терминологии и традиционной для русскоязычной литературы. Обсуждены наиболее дискуссионные проблемы в понимании феномена эпифитизма в мировой литературе.
Рассмотрены механизмы существования растений, порвавших с наземными источниками минерального питания и воды. Изложена проблематика и степень изученности САМ (crassulacean acid metabolism) у эпифитов в контексте их ксероморфоза. Рассмотрен механизм и функциональная
роль образования подвешенных почв. Отражены существующие теории и дискуссионные проблемы минерального питания эпифитов, в частности азотного питания. Обобщены различные биологические аспекты освоения крон: диаспорология, строение эпифитных сообществ и экосистемная роль эпифитов.
... Suspended soils serve as a biodiversity depository, and function in a similar way to the upper horizons of more northern forest ground soils. This idea is confirmed by the fact that, on the whole, the biodiversity of suspended soils is greater than that of terrestrial soils in the tropics [17][18][19][20]49]. However, our studies have only partially confirmed this data. ...
Microbial biodiversity parameters for tropical rainforests remain poorly understood. Whilst the soil microbiome accounts up to 95% of the total diversity of microorganisms in terrestrial ecosystems, the microbiome of suspended soils formed by vascular epiphytes remains completely unexplored. Samples of ground and suspended soils were collected in Cat Tien National Park, southern Vietnam. DNA extraction and sequencing were performed, and libraries of 16s rDNA gene sequences were analyzed. Alpha diversity indices of the microorganisms were the highest in the forest ground soil. In general, the microbiological diversity of all the soil types was found to be similar at the phylum level. Taxonomic composition of the bacterial communities in the suspended soils of plants from the same species are not closer than the taxonomic compositions of the communities in the suspended soils of different plant species. However, the beta diversity analysis revealed significant differences in the movement of mineral elements in terrestrial versus suspended soils. Our data showed that the suspended soils associated with vascular epiphytes were a depository of unique microbiological biodiversity. A contributing factor was the presence of large amounts of organic matter in the suspended soils—deposits collected by the epiphytes—which would have been degraded by termites if it had reached the ground. Further, the nutrient content of the suspended soils was prime for soil respiration activity and taxonomic microbial community biodiversity
... Mites and springtails are highly responsive to water availability (Huhta and Hänninen, 2001;Convey et al., 2003), and soil moisture (or lack thereof) is a strong environmental filter for soil fauna (Siepel, 1996;Lindo et al., 2012). For oribatid mites in particular, soil moisture regimes are fundamental factors influencing the diversity, abundance and distribution of oribatid mites (Siepel, 1996;Lindo and Winchester, 2007) where drier conditions typically lead to reductions in both abundance and richness. Precipitation, or more specifically pluviosity (i. ...
Soils systems provide essential ecosystem functions and services performed by a hyperdiverse array of fauna, but how soil communities respond to climate change remains an understudied topic. Although previous long-term studies have found variable effects of climate change manipulations on soil communities, precipitation often yields strong responses from fauna. In this study we used a field-based experiment to test how soil communities respond to active warming (+4 • C) and elevated atmospheric CO 2 concentrations (800 ppm) in the boreal forest over two consecutive years in a full factorial experimental design. We sampled and identified soil fauna across multiple taxonomic groups to determine how species abundance, richness, diversity, evenness, and community composition were affected by these simulated global climate change factors. Fauna were minimally affected by experimental treatments in the first year of sampling. However, in the second year of treatment, richness and diversity increased and soil community composition shifted as oribatid mites responded to both warming and elevated CO 2 and springtails responded to warming treatments. We propose that the enhanced response of soil communities in the second year of experimental treatment was due to greater than normal precipitation, suggesting that annual variability in weather conditions can influence soil fauna response to climate change.
... Так, в начале сухого сезона (более недели без дождя) сырая масса ЭМ "гнезд" содержала 203% депонированной влаги, моховых подушек -125%, а моховых "бород" всего 28% (от сухого веса ЭМ). Подвешенные почвы ЭМ также являются местообитанием множества беспозвоночных [35,36]. Кроме того, высокая влагоудерживающая способность подвешенных почв обеспечивает протекание в них процессов гумификации [37]. ...
Исследовали эпифиты в искусственных лесопосадках, имитирующих смешанный тропический лес Южного Вьетнама. По числу видов эпифитные орхидные (6 видов) лучше представлены, чем папоротники (5 видов), но последние превалируют по количеству особей. Сравнение флористического состава эпифитного сообщества посадок с близлежащим материнским лесом (индекс Стугруна-Радулеску ρsr = 0.68), а также двумя другими лесными массивами Южного Вьетнама (лесхоз Ма Да и о. Фу Куок; ρsr = 0.61 и 0.71 соответственно), не выявило существенного сходства. Однако полученные данные свидетельствуют о том, что за 20 лет в искусственных лесопосадках сформировалось относительно сложное эпифитное сообщество, способное накапливать в кронах до 100 кг/га депонированного органического вещества и компонентов минерального питания растений.
... Moss cushions with additional planting of orchids of the dry season (over a week without rain), the wet EM weight of trash baskets and moss cushions contained 203 and 125% of deposited moisture, respectively, while that of moss beards contained only 28% (of the dry EM weight). Suspended EM soils also serve as a habitat for many invertebrates [35,36]. In addition, the high moisture-retaining capacity of suspended soils results in humification processes in these soils [37]. ...
Epiphytes in man-made forests simulating a mixed tropical forest of South Vietnam are studied. With respect to the number of species, epiphytic orchids are better represented than ferns (six vs. five species); on the other hand, the latter prevail in the number of individuals. A comparison of the floristic composition of the epiphytic community of plantations with a nearby primary forest (Stugrun-Rădulescu index ρ sr = 0.68) and two other South Vietnam forests (Ma Da Forestry and Phu Quoc Island; ρ sr = 0.61 and 0.71, respectively) did not reveal significant similarities. However, these data indicate that a relatively complex epiphytic community , which can accumulate up to 100 kg/ha of deposited organic matter and plant mineral nutrients in crowns, has been formed in the man-made forests over 20 years.
... Either way, they are generally found in the presence of decaying plant material (36,37). Oribatids are generally free living in the upper soil layers, but Phthiracaroidea are commonly found within fallen leaves or conifer needles (37), and ground-dwelling species can be found up to 4 m from the ground on live tree trunks (38) with a clear gradient of community species composition ascending the trunk (39). ...
Significance
Aquatic organisms are rarely found in amber, but when they occur they provide invaluable evidence for the better understanding of amber taphonomy and past ecosystems. We report an ammonite and several marine gastropods alongside a mixed assemblage of intertidal and terrestrial forest floor organisms in mid-Cretaceous Burmese amber. Our discovery indicates that the Burmese amber forest was living near a dynamic and shifting coastal environment. The ammonite also provides supporting evidence for the age of the amber, which is still debated, and represents a rare example of dating using fossils present inside the amber.
... Although the relationships between the litter decomposition and soil microarthropods have been widely studied [54], little is known about the changes in Mesostigmata mite communities in the short term. Repeated measurements of litter mass loss and fauna extraction allow checking whether the changes in species number and abundance in decomposed litter is successional, as has been proposed by Usher [55], seasonal or driven by abiotic factors [24]. Interestingly, our study revealed that the mean species richness in the 'soil mite pool' was higher than in the decomposed litter, regardless of tree species. ...
Replacement of native deciduous forests by coniferous stands was a common result of former European afforestation policies and paradigms of forest management and led to considerable ecological consequences. Therefore, the most popular management strategy nowadays in multi-functional forestry is the re-establishment of mixed or broadleaved forests with native species on suitable habitats. However, our knowledge about the effects of tree species introduced into coniferous monocultures on soil mesofauna communities is scarce. We investigated abundance, species richness and diversity of Mesostigmata mite communities in decomposed litter of seven broadleaved (Acer platanoides L., A. pseudoplatanus L., Carpinus betulus L., Fagus sylvatica L., Tilia cordata Mill., Quercus robur L., Q. rubra L.) and four coniferous (Abies alba Mill., Larix decidua Mill., Picea abies [L.] Karst., Pinus sylvestris L.) species. We collected 297 litterbags after 6, 12 and 18 months of exposition in Scots pine (Pinus sylvestris) monocultures in Siemianice Experimental Forest (SW Poland). Generally, species richness and diversity in litter samples were much lower than in the soil mite pool. The highest abundance was found in P. sylvestris and A. alba litter, while the lowest was found in A. platanoides. The most abundant families were Zerconidae, Parasitidae, Veigaiidae, and Trachytidae. Our study revealed that neither species richness nor diversity were affected, but that mite abundance was affected, by the tree species (litter quality). The mite communities were similarly comprised in both high-and low-quality litter and mite abundance decreased during the decomposition process in nutrient-poor Scots pine forests. Moreover, few mite species benefited from the decomposed litter. Additionally, a litter of various tree species was inhabited mainly by eu-and hemiedaphic mite species. Mite assemblages in A. alba, P. sylvestris, and Q. robur litter had higher abundances. Exposition time seems to be an important driver in shaping the mite community during the early stages of litter decomposition.
... Yet, significant differences were seen in the richness and abundance of microarthropods associated with hummock and hollow microtopologies. Microarthropods are sensitive to moisture regimes and humidity of microhabitats, with low moisture conditions limiting species richness, abundance, and diversity (Siepel 1996;Materna 2000;Pflug and Wolters 2001;Lindberg 2003;Lindo and Winchester 2007) in many ecosystems. Oribatid mites as the dominant microarthropod in peatland systems (Silvan et al. 2000;Laiho et al. 2001;Lindo 2015) showed similar results to Collembola suggesting many microarthropod groups are similarly responding to microclimate conditions or latent differences in resource availability. ...
In boreal peatlands, low decomposition rate is the underlying cause of carbon sequestration. Decomposition of litter can be affected by factors relating to soil moisture and temperature, the quality of the litter, and by the biotic decomposer community, among others. Exploring how these drivers interact will provide better understanding of carbon dynamics in boreal peatlands. We measured the decomposition of three common peatland plant functional types (moss, sedge, shrub), and associated microarthropod communities using litterbags placed in hollows (wet depressions) and hummocks (dry, raised areas) of a boreal peatland in Ontario, Canada. Decomposition was significantly different between all plant litter types, and greatest in sedge, but was not significantly different between hummock and hollow microhabitats. The decomposer community displayed an opposite pattern, significantly affected by microhabitat where richness and abundance of microarthropods was greater in hollows than hummocks. Oribatid mites were the dominant microarthropod with respect to both richness and abundance. Plant litter type did not affect community structure in hollows, but was a determinant of oribatid dominance in hummocks. These results suggest that abiotic environmental conditions are the main drivers of community structure for decomposers, while plant litter quality is a more important determinant of decomposition dynamics in boreal peatlands.
... Due to its special and protected position, such a lignoform is likely to host very specific flora and fauna (vertebrates and invertebrates), (see e.g. Aubert de La Rüe et al., 1954;Lindo and Winchester, 2007). This type of humus form could be easily related to the concept of suspended soils discussed for example by Paulian (1988) or Gobat et al. (2010). ...
Among the many studies devoted to deadwood, very few have considered it in a broader ecosystemic context, especially in relation to the underlying humiferous topsoil. In order to fill this gap, we detail here the concept of lignoforms, humus forms strongly linked to deadwood and mostly ignored by humus forms specialists. After presenting the main characteristics of deadwood, the main actors involved in its life cycle and its important and varied roles in many ecosystems, we explain how to describe and study lignoforms. We also propose new diagnostic horizons for these particular humus forms, as well as a classification system, including an identification key (see Appendix F Identification key for lignoforms). Finally, we discuss some important issues pertinent to continuing to improve knowledge of these common but little studied humus forms.
... The high proportion of Brachychthoniidae and Oppiidae species in April 2013 may be due to massive hatching of their eggs during the well-known spring-peak of oribatid abundance 41 . However, the recorded differences in the overall abundance between two sampling occasions are within the known range of abundance and diversity variance across different seasons and years 42,43 . ...
In a dry heathland ecosystem we manipulated temperature (warming), precipitation (drought) and atmospheric concentration of CO 2 in a full-factorial experiment in order to investigate changes in below-ground biodiversity as a result of future climate change. We investigated the responses in community diversity of nematodes, enchytraeids, collembolans and oribatid mites at two and eight years of manipulations. We used a structural equation modelling (SEM) approach analyzing the three manipulations, soil moisture and temperature, and seven soil biological and chemical variables. The analysis revealed a persistent and positive effect of elevated CO 2 on litter C:N ratio. After two years of treatment, the fungi to bacteria ratio was increased by warming, and the diversities within oribatid mites, collembolans and nematode groups were all affected by elevated CO 2 mediated through increased litter C:N ratio. After eight years of treatment, however, the CO 2-increased litter C:N ratio did not influence the diversity in any of the four fauna groups. The number of significant correlations between treatments, food source quality, and soil biota diversities was reduced from six to three after two and eight years, respectively. These results suggest a remarkable resilience within the soil biota against global climate change treatments in the long term.
... No. Familias/uso Riqueza de familias de ácaros oribátidos presente en los diferentes usos de suelo en el corregimiento Obonuco (Pasto, Nariño disCusiÓn La mayor abundancia y diversidad de familia de oribátidos se encontraron en el bosque, este hábitat es propicio para el desarrollo de estos organismos según LINDO & WINCHESTER (2007), quienes mencionan que la constante caída de hojas aumenta paulatinamente la capa de hojarasca, creando un hábitat favorable para la permanencia de los ácaros. Además, PRIETO et al. (2005) manifiestan que el bosque es un ambiente imprescindible para su proliferación y contribuye al proceso de descomposición de la materia orgánica. ...
... Members of this family can be found in soils and litter layers, but they also represent one of the mite groups more frequently found on tree canopies [103,120]. They are considered to be secondary decomposers due to their preferential feeding on fungi, but some species are predators on other small invertebrates [76,108]. ...
Peatlands are typically reported to sustain low diverse soil fauna communities due to cold temperatures and waterlogging conditions which restrict biological activities. However, very few studies have undertaken a comprehensive survey of soil invertebrate communities in these systems and in most cases the information available is only based on very few records taken on few sampling occasions. In the case of arthropods, difficulties in obtaining accurate identifications and quantifications due to the fact that some groups only stay in the soil for short periods of time, add complications to their study. Their ecological role as litter transformers and predators is determinant in the decomposition and turnover of soil organic matter. Therefore, in this chapter we provide a detailed study of the Arthropod community from two contrasting climatic and vegetational peatland sites to evaluate their habitat selection and their responses to changes in environmental conditions. The Arthropoda community at the two investigated upland peatlands was represented by three subphyla (Chelicerata, Myriapoda and Hexapoda), but macroarthropods only accounted for 1% of the total number of invertebrates collected. Our results indicate that habitat characteristics can have a strong influence on the structure of the Arthropoda community within a particular peatland area, both in terms of population numbers and diversity. Overall, significant higher abundances of most groups (exceptions were Aranea, Pseudoescorpionida, Opilionida and Insecta) were observed at the drier locality (Chan do Eume) than at the most oceanic and wettest site (Chan do Lamoso). Although at both localities Oribatid mites dominated the arthropod community and with Entomobryomorpha collembolans and Prostigmata mites being the two following more abundant groups, their percentages differed slightly between sites and thus, at Chan do Eume oribatids represented 58% of the total numbers, Entomobryomorpha 17% and Prostigmata 11%, whereas at Chan do Lamoso they followed the order Oribatida (37%) > Entomobryomorpha (29%) > Prostigmata (7%). Interestingly, 15 out of the 48 Acari families and half of the insect orders identified were only recorded at one site; in addition, proturans and symphylans were only found at the most continental locality but pseudoscorpions and opilions at the most oceanic one. These differences in the Arthropod community could be partly related to the particular microclimatic conditions at each site, with a strong effect on soil moisture, but also to the different vegetation. Our results suggest that more frequent waterlogged conditions and marine proximity have negative effects on the two dominant groups in these systems (mites and collembolans) and therefore, alterations in the nutrient cycling dynamics associated to climatic changes are anticipated.
... Litterfall provides a major pathway for nutrient and energy transfer from plants to soil (Coxson and Nadkarni 1995;Lindo and Winchester 2007). This flux has been related to forest productivity, nutrient cycling, and the dynamics of soil organic matter (Edmonds and Murray 2002;O'Keefe and Naiman 2006). ...
The amounts and ecological importance of epiphytic litterfall has often been overlooked in forest ecosystem studies. However, epiphytes participate in whole-ecosystem dynamics by capturing and retaining nutrients from atmospheric sources and transferring these nutrients to other ecosystem components. We quantified epiphytic litterfall under the canopy of mature bigleaf maples (Acer macrophyllum Pursh) and compared it with other litter components in an old-growth temperate rainforest in Washington State. Total litterfall during one year was 4760 kg·ha−1, with the greatest contribution from bigleaf maple leaves. Of the total litter input, 546 kg·ha−1 consisted of epiphytic litter, equivalent to 12% of total fine litter input, the highest contribution of epiphyte litterfall documented for this type of forest. Compared with other studies in the Pacific Northwest, our estimations of conifer needle inputs relate to the location of the littertraps. Bigleaf maple leaves dominated carbon (C) and nitrogen (N) returns in litter; epiphytic litterfall contributed 240 kg·ha−1·year−1 of C (~11% of total C inputs) and 5.7 kg·ha−1·year−1 of N (~11% of total N inputs) to the forest floor. Inputs of N from epiphytes and bigleaf maple litter under the canopy of this tree could be important in augmenting N in this old-growth ecosystem. © 2015, National Research Council of Canada, All Rights Reserved.
... Scytonema was the main free-living cyanobacterium and its scytonemin-rich sheath may have contributed to its success here. Cyanobacterial density was considerably greater on epiphytic mosses than those on the forest fl oor and the authors suggested that this might result from N transfer from the epiphyllous communities to the ground underneath, since nutrient concentrations in suspended soil underlying epiphytic bryophytes are known to be higher than on forest fl oor soils at another western British Columbia site (Lindo and Winchester 2007 ) . There are apparently no similar studies in tropical rain forests, but it should be possible to get some idea as to whether cyanobacteria are frequent among epiphyllous mosses by checking herbarium material. ...
Subaerial cyanobacterial communities are conspicuous on the surfaces of many environments subject to considerable water stress, though the communities are increasingly likely to be endolithic the greater the water stress. In temperate regions the communities tend to be best developed on calcareous surfaces, especially in the case of strict epiliths. However, the contrast with non-calcareous surfaces is less obvious in the tropics, where many examples of well developed cyanobacterial communities have been reported from non-calcareous surfaces. Detailed floristic lists often include species of Gloeocapsa, Pseudocapsa, Phormidium, Microcoleus, Tolypothrix, Scytonema, Dichothrix and Stigonema, and also Nostoc from the more horizontal surfaces. Almost all taxa have a well developed extracellular matrix, which includes scytonemin or other coloured UV-protective pigments in all except the most shaded environments. Although the general effects of differences in environmental factors such as temperature, light, UV stress, pH, CO2 and mineral nutrients are understood quite well, relatively little is known about the detailed responses to different combinations and periodicities of these factors.
... Also, these ants are considered highly aggressive and invaders, consequently forest management may promote their abundance. In the unmanaged forest Haplozetidae sp. was abundant, and mites (Acari) contribute to decomposition and nutrient cycling processes because of their interactions with the microbial community (Moore et al. 1988, Lindo andWinchester 2007). ...
We analyzed the effect of selective logging on litter fauna parameters (abundance, richness and diversity) and litter decomposition (remaining dry mass) over time in a temperate pine-oak (Pinus spp.-Quercus spp.) forest in central México. An unmanaged and a managed forest were compared using a litter bag field experiment. Litter fauna was quantified to the levels of families and morphospecies. Litter fauna abundance, richness and diversity were higher in the unmanaged forest. The remaining dry mass of litter and the decomposition rates were statistically different between the two forests, suggesting that selective logging practices reduce decomposition processes. The remaining dry mass of litter was negatively correlated with fauna richness in the managed forest, and with both morphospecies richness and diversity at the unmanaged forest; indicating that as biodiversity increases, more litter might be decomposed. Both litter fauna diversity and the litter decay processes were better preserved in the unmanaged site, as compared with the selective logged forest. Our study reveals that leaving some pine-oak forest patches unmanaged is important for the protection of their biodiversity.
... Members of this family can be found in soils and litter layers, but they also represent one of the mite groups more frequently found on tree canopies [103,120]. They are considered to be secondary decomposers due to their preferential feeding on fungi, but some species are predators on other small invertebrates [76,108]. ...
Invertebrates are common in marine and freshwater ecosystems and key elements in processes such as trophic dynamics and nutrient recycling. At the present time we have a limited knowledge of their diversity and how they have evolved over time. A key element of study in this book, are the current efforts to produce revised classificatory systems which include modern approaches and an update of the current taxonomical system. Another topic discussed in great detail is the relation of invertebrates and their contribution to biodiversity in terms of unique species per habitat. "Invertebrates: Classification, Evolution and Biodiversity" represents an effort to show the relevance of this unique group of living species and the current efforts to better understand them. This book presents a well balanced set of chapters in which a detailed review of the classification of poorly known groups (such as freshwater arthropods, oligochaetes, and marine ascidians) are studied. Another set of chapters are devoted to understanding the associated biodiversity of invertebrates in marine ecosystems and how they respond to environmental variables. Biogeographical comparisons and evolutionary fractal analysis close the contributions and provide a high standard of knowledge towards the goal of this book. This book also discusses the role of invertebrates in coastal systems and provides key investigation for undergraduate and graduate students and researchers and professional researchers who are interested in ecology and evolution.
Purpose : Old-growth forests in the Pacific Northwest host a variety of epiphytes on their branches and stem. Given the common and often large epiphytic biomass associated with Acer macrophyllum (Pursh ) in this region, we evaluated how seasonal weather changes and urbanization (metal and nitrogen deposition), affect canopy epiphytic N2 fixation in the Hoh Rainforest of the Olympic Peninsula and in urban parks and forests in Seattle.
Methods : We collected Isothecium stoloniferum (Brid.) samples from both the Hoh Rainforest and Seattle at four periods from April 2016 through January 2017. Moss-associated N2 fixation rates were measured in the laboratory using the acetylene reduction assay and trace metal concentrations in the moss were analyzed using NO3 + H2O2 digestion.
Results : We found levels of N2 fixation were highest during the spring sampling period. Elevated levels of heavy metals were observed in I. stoloniferum samples collected in the urban canopies in Seattle, suggesting N2 fixation is sensitive to the bioaccumulation of heavy metals. In A. macrophyllum canopies, I. stoloniferum was found to yield 1.13 kg N ha⁻¹ yr⁻¹ in the Hoh Rainforest and only 0.009 kg N ha⁻¹ yr⁻¹ in Seattle.
Conclusions : These results highlight a rarely explored source of biological N2-fixation in temperate rainforests and suggest that epiphytic N2-fixation may contribute bio-available nitrogen in secondary successional A. macrophyllum stands.
Background
In the last decades, Southeast Asia has experienced massive conversion of rainforest into rubber and oil palm monoculture plantations. The effects of this land-use change on canopy arthropods are still largely unknown. Arboreal Collembola are among the most abundant canopy arthropods in tropical forests, potentially forming a major component of the canopy food web by contributing to the decomposition of arboreal litter and being an important prey for canopy arthropod predators. We investigated abundance, richness, and community composition of, as well as the influence of a series of environmental factors on, canopy Collembola communities in four land-use systems in Jambi Province, Sumatra, Indonesia: (1) lowland rainforest, (2) jungle rubber (rubber agroforest), and monoculture plantations of (3) rubber and (4) oil palm.
Results
Using canopy fogging in 32 research plots in both the dry and rainy seasons in 2013, we collected 77,104 specimens belonging to 68 (morpho) species. Generally, Collembola communities were dominated by few species including two species of the genus Salina (Paronellidae; 34% of total individuals) and two species of Lepidocyrtinae (Entomobryidae; 20%). The abundance of Collembola in lowland rainforest (53.4 ± 30.7 ind. m ⁻² ) was more than five times higher than in rubber plantations, and more than ten times higher than in oil palm plantations; abundances in jungle rubber were intermediate. Collembola species richness was highest in rainforest (18.06 ± 3.60 species) and jungle rubber (16.88 ± 2.33 species), more than twice that in rubber or oil palm. Collembola community composition was similar in rainforest and jungle rubber, but different from monoculture plantations which had similar Collembola community composition to each other. The environmental factors governing community composition differed between the land-use systems and varied between seasons.
Conclusions
Overall, this is the first in-depth report on the structure of arboreal Collembola communities in lowland rainforest and agricultural replacement systems in Southeast Asia. The results highlight the potentially major consequences of land-use change for the functioning of arboreal arthropod food webs.
A variety of techniques are available to access forest canopies and to sample canopy insect diversity. Canopy access methods include ropes, towers, walkways, balloons, and cranes. Selection of canopy access method depends on forest type, cost and portability of equipment, access to lower or upper canopy, interior or periphery of tree crowns, and representation of single or multiple trees. Sampling techniques include branch beating, interception traps, branch bagging, canopy knockdown, and bait stations. Selection of sampling method depends on research objectives, e.g., representation of target or multiple taxa, flying or sedentary insects, and nocturnal or diurnal insects. All sampling techniques are biased toward particular groups, e.g., interception traps collect primarily flying insects, light traps collect nocturnal insects, branch bagging collects insects on the branch at the time of sampling, etc. Therefore, combinations of sampling techniques are recommended if the research objective is to represent total arthropod diversity.
As the upper section of the Mekong River Basin, the vegetation quality of the Lancang River Basin (LRB) and the related ecological functions are critical for the whole basin. With time-series Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2000 to 2015 and local daily climatic data since 1976, their vertical interaction differences were identified. The results showed that the spatial variation in Normalized difference vegetation index (NDVI) of grassland and forest were sensitive to elevation. The NDVI value in the southern area at elevations less than 3000 m was more than 0.80 and decreased to 0.30-0.60 with elevations higher than 4500 m. The general vegetation quality showed a positive trend under climate change over 16 years. The M-K test of daily precipitation and temperature from 12 local weather stations showed that the basin temperature varied more significantly than precipitation. The temporal correlation between NDVI with precipitation as well as temperature at each pixel indicated that temperature was the dominant factor affecting grassland and forest dynamics in the LRB. The interaction between vegetation and climate was more sensitive at elevations lower than 3000 m. Based on the RCP4.5 scenario, the future temperature distribution was predicted, and its impact on NDVI was simulated at the pixel scale. Under future drier and warmer climate conditions, the responded NDVI in the upper stream with higher elevation may increase soil erosion and decrease streamflow. The NDVI in the downstream area will be improved and be able to adapt to the related climate impacts. Because of the large amount of water and biomass in this basin, higher temperatures will accelerate the decomposition of forest foliar litter. Thus, more organic carbon and forest diffuse pollution will be discharged into the water, potentially affecting the water quality of the whole basin.
The soil arthropods are an important component of the soil biota for their species diversity, function, and as tool to evaluate the habitat conservation state. The conservation state of three sectors in an ecosystem of high mountain (Socha, Tasco and Socotá in Boyacá, Colombia) was evaluated measuring alpha and beta diversity of epigean arthropods assemblage in particular Acari and Collembola. Pitfall traps were installed on transects for each sector; the alpha diversity was measured through Berger-Parker index and a gamma-binomial model was used to obtain a parameter a, which describes the fitting to species abundance distribution. The species diversity estimation was established with coverage-based rarefaction and extrapolation curves, and the beta diversity was measured in species replacement and richness difference. The alpha diversity did not show statistical differences between sectors, but with the highest species richness in the sector of Socotá. The a parameter indicated that the sector of Socotá is the better conserved; similar to that obtained with Acari and Collembola. The spatial turnover or species richness difference showed changes with respect to the sector and taxonomic group (Acari or Collembola), explained by vegetation structure, erosion, and aggregate distribution of epigean arthropods. The species replacement did the main contribution to total beta diversity by sectors while in Acari and Collembola the species replacement was highest in Tasco in contrast to the richness difference in Socha and Tasco. The utility of epigean arthropods to evaluate the soil quality and the partition of the beta diversity in their components was discussed. © 2017, Sociedad Colombiana de Entomologia. All rights reserved.
The aim of this work was to make an inventory of oribatid mite families associated to six land uses: a silvopasture arrangement, a potato crop in rotation with pastures, a potato crop, a bank forage protein, a plot of three grasses and clover mixed and a secondary forest. The variables abundance, richness and diversity index were measured; data was subject to variance analysis using Fishers least significant difference test (LSD). Nine families of the Oribatida order: Ceratozetidae, Mochlozetidae, Oppidae, Haplozetidae, Galumnidae, Plasmobotidae, Pheroliodidae, Tectocepheidae and Euzetidae were identified; the first three families were the most abundant, representing more than 70% in all land use systems. The ecosystem that showed the highest abundance and biodiversity of oribatid mites was the secondary forest ecosystem in relation to the different systems. The potato system presented fewer species. Also the silvopasture system, the protein bank and the forest had higher values in relation to species diversity compared to potato system, in which a negative effect of soil mite fauna possibly due to high use of agrochemicals such as fertilizers and pesticides.
People, like other large terrestrial mammals, tread the surface of the Earth and we know best the aboveground half of the ecosystems we inhabit. Forests, grasslands, meadows, fields, deserts and cities squat on the surface of the earth, but each has its shadow existence belowground. Less than half of the energy fixed by the sun is respired by the plants, animals and microbes that live aboveground: most falls into the living system we call soil (Macfadyen 1963). Soils are well known for their extraordinary biological diversity (Wardle 2006) and, more than any other habitat, this largely belowground system is the empire of mites.
Dothistroma septosporum is a serious foliar pathogen of pines in Britain. To determine the contribution of spores produced on abscised needles to the D. septosporum inoculum load in a forest environment, survival of the fungus was investigated in commercially grown plantations of Corsican pine (Pinus nigra subsp. laricio) in southern England. The fungus persisted for longer in abscised needles retained in the canopy compared with needles on the litter layer of the forest floor. High relative humidity had a significant negative effect on persistence in the canopy needles, highlighting the effect of moisture on rates of microbial decay. The median lethal time 50 (LT50) of infective propagules from needles in the litter layer was 20 to 28 days, whereas for needles suspended in the canopy it was 34 to 48 days. Microsatellite markers revealed that the population of D. septosporum deemed persistent (i.e., recovered from abscised needles after exposure for 28 to 32 weeks) was similar to the general population of D. septosporum in the forest stand (i.e., isolates recovered from attached needles and after exposure for only 4 weeks). Overall, abscised needles with acervuli of D. septosporum contribute only moderately and for a limited time to inoculum levels of the pathogen in an infected forest stand.
Poised between soil and sky, forest canopies represent a critical point of exchange between the atmosphere and the earth, yet until recently, they remained a largely unexplored frontier. For a long time, problems with access and the lack of tools and methods suitable for monitoring these complex bioscapes made canopy analysis extremely difficult. Fortunately, canopy research has advanced dramatically in recent decades. Methods in Forest Canopy Research is a comprehensive overview of these developments for explorers of this astonishing environment. The authors describe methods for reaching the canopy and the best ways to measure how the canopy, atmosphere, and forest floor interact. They address how to replicate experiments in challenging environments and lay the groundwork for creating standardized measurements in the canopy-essential tools for for understanding our changing world.
Species in the oribatid mite genus Autogneta are primarily Palaearctic, with a few, mainly unidentified records from North America. Strong sexual dimorphism is reported in the genus for the first time; it is expressed by a posterior porose region on the male notogaster that in some species is associated with modifications of notogastral setae h<sub>1 </sub>and p<sub>1</sub>. Herein, I describe 3 new dimorphic Autogneta species from North America, based on adult specimens: A. aokii sp. nov. and A. schusteri sp. nov., from California, USA, and A. flaheyi sp. nov., from British Columbia and Alberta, Canada. New diagnoses for 2 other dimorphic species, the type species Autogneta longilamellata (Michael) and A. amnica Jacot, are presented that accommodate their previously unreported dimorphic males. Autogneta flumengalei Jacot is recombined as Conchogneta flumengalei (Jacot) comb. nov. Finally, I give a key to adults of Autogneta species known from North America.
In the Mediterranean region of Chile, populations of the threatened tree Beilschmiedia miersii have been strongly affected by anthropic disturbances, causing a critical state of conservation. Herbivory has been proposed as the main factor that currently limits the regeneration of this species. We studied the effect of large vs. small herbivores on seed and seedling survival of B. miersii under two contrasting habitat conditions (forest and shrubland), using plots with fenced enclosures which differentially excluded mammalian
herbivores according to body size. Results show that herbivory had a significant negative effect on B. miersii. Both large and small herbivores had a significant negative effect on seeds and seedlings in the shrub habitat. In the forest habitat small herbivores had a
significant negative effect only on seeds. Our results suggest that different herbivores can have varying effects on seed and seedling survival, but these effects can vary spatially, probably due to different herbivore assemblage of each habitat. Results suggest that
restoration plans for B. miersii need to be adjusted according to local conditions.
This study focused on two questions relevant to ecophysiology: Do distributions of animal species track shifting microclimatic mosaics under Þeld conditions? Do distributions on different levels of spatial resolution (different "scales") consistently modify a speciesÕ access to heat or humidity? I counted the arthropods on the bark of exposed tree trunks in northern Germany with a 10 lens and investigated how the dominant species (collembolans, psocopterans, isopods, a linyphiid spider, and an oribatid mite) used climatic patterns at various scales. These included mesoclimatic patterns and shifting microclimatic patterns such as microrelief, trunk faces, and trunk/mesoclimate differences. Bias owing to changing frequency of microhabitats, or to redistri-butions of animals between microhabitats was avoided. I also investigated the effects of climatic patterns on heat and humidity levels at the bark surface. The distributions of all species, except the psocopterans, similarly tracked shifting microclimatic mosaics and mesoclimates. The distributions of most species modiÞed their access to heat or humidity consistently at several mutually independent scales. The remaining species seemed to be restricted in their climate use by sensory or metabolic limitations.
As compared with the control treatment with bacteria only, the nitrogen mineralization rate was increased in the presence of nematodes and mites and in the presence of nematodes only, in the latter case after an initial stage of nitrogen immobilization. The results indicate that the mites caused the nematode population to increase less rapidly than in their absence. They largely prevented nitrogen immobilization in the presence of the nematodes and also retarded the release of nitrogen in the presence of the nematodes. -from Authors
Oribatid mite abundance,species richness,and community composition in annual litter fall were compared betweenthe high canopy of an ancient temperate rainforest and the forest floor to evaluate whether litterfall, including mossdebris, is a dispersal vector for these organisms. Oribatid mites were extracted from litterfall collected from canopy(30)m and ground (1)m litter traps associated with six western red cedar trees in the Walbran Valley on the southwestcoast of Vancouver Island, Canada, over 3, 6, and 12 months. Total annual litter input was not significantly differentbetween canopy and ground traps, as high amounts of litter were associated with both habitats. Litter compositiondiffered between the two habitats and cumulative input over larger spatial scales may prove to be appreciablydifferent.Fifty-seven species of oribatid mites were associated with total litterfall collected in canopy and ground trapsover 12 months.Species richness over the entire sampling period was similar between canopy and ground habitats,but oribatid mite species composition differed significantly, and is most likely related to litter composition and the initialsource of litter. Oribatid mite abundance(number of individuals per gram dry weight)associated with litterfall waslow compared to suspended soil habitats, and not significantly different between litter accumulation in ground andcanopy traps. Nevertheless, a general trend of high litter input and high species richness associated with litterfall incanopy habitats, combined with high disperser survivorship, suggests dispersal vectors such as moss mats are importantfor maintaining arboreal oribatid mite communities
In some tropical forests, organic matter derived from epiphytic plants accumulates as mats on tree branches. Microbial characteristics relating to the cycling of C and N were studied in this canopy organic matter (COM) and in the forest floor of a tropical montane forest in Costa Rica. COM was found to have high microbiat activity which was. in general, similar to the forest floor H (FF-H) horizon. The concentration of microbial biomass C was 2650, 2670 and 1950 μg g−1 soil in COM, FF-H and FF-Al, respectively. Biomass N, laboratory CO2 evolution and laboratory N mineralization were also higher or similar for COM relative to the forest floor.In contrast to the H and Al horizons of the forest floor, nitrification was not detectable or only very low in COM during laboratory and field incubations. The potential for denitrification, as evidenced by the decline in added NO−1 relative to NH+4 during laboratory incubation, was higher in the forest floor than in the canopy.Microbial respiration and biomass in COM and the forest floor responded more to C (as glucose) than N (as NH4NO1) amendments. Microbial immobilization of added N appeared to be higher in the forest floor than in COM, although the microbial population in all materials readily immobilized inorganic N in the presence of glucose.The total pool of COM in this forest is estimated to be between 1000 and 2000 kg ha−1. From this, a preliminary estimate of 0.7 kg ha− of N immobilized in microbial tissue can be calculated. Because of their high biomass and activity, microorganisms in the canopy could be important in regulating N availability in this forest.
The effects of partial and clear-cut harvesting on forest floor physical, chemical, and biological properties, forest floor mesofauna, and nutrient cycling were investigated in conifer- and deciduous-dominated stands of Alberta's mixedwood boreal forest. Forest floor samples were collected 2.5 years after harvest from clearcuts, strip-cut corridors in a partial cut, green tree retention patches in a partial cut, and uncut control sites. Partial cuts showed intermediate decreases in annual litter input and NH4-N between uncut and clear-cut sites of both the deciduous and conifer stands, as did microbial biomass, PO4-P, mesofauna abundance (total, Acari, and Collembola), and fine root biomass in the conifer stands. In the deciduous stands, microbial biomass and fine root biomass in partial- and clear-cut treatments were not significantly different, but were significantly reduced compared with the uncut controls. Mesofauna abundance was reduced in the corridors of the partial-cut treatment compared with partial-cut patch, clear-cut, and uncut treatments. In both deciduous and conifer stands, NO3-N was elevated in the partial-cut corridors and clearcuts compared with partial-cut patch and uncut treatments. Findings from this study show that negative impact to forest floor properties associated with clear-cut harvesting may be reduced in partial-cut harvesting systems.
The objective of this study was to improve our understanding of the role of soil invertebrates in the breakdown of litter, cycling of nitrogen, and growth of seedlings in forests of British Columbia by comparing two experimental approaches. First, in the laboratory, breakdown of birch leaves was slightly higher in the presence of millipedes in the microcosms of forest floor collected from two coastal forests. Presence of smaller animals (mesofauna) and contaminant Diptera larvae did not hasten litter breakdown in microcosms made from forest floor from either a sub-boreal or a coastal forest. In general, inorganic nitrogen release was higher in the presence of fauna, but results were highly variable. Growth of seedlings was slightly greater in the coastal microcosms that included millipedes. In the second approach, a field experiment was conducted using intact forest floor cores enclosed with one of three mesh sizes (54 µm, 1 mm, and 5 mm) and defaunated with liquid nitrogen. Comminution of birch leaves, and to some extent, greater inorganic nitrogen release occurred in sacs that allowed access to larger animals compared with sacs with fine mesh that excluded them. Although differences among treatments were small, the results from both approaches agree and indicate that soil invertebrates increase rate of breakdown of forest litter and cycling of nutrients in coastal forests.
Reviews soil arthropods from the perspectives of both community and systems ecology, suggesting that arthropods contribute significantly to decomposition and nutrient cycling; have an integral role in maintaining and shaping microbial activity and community structure; and are important mediators of food web stability. -from Authors
The effects of litter quality and climate on decomposition rates of plant tissues were examined using percent mass remaining (MR) data of 10 foliar litter types and 1 wood type during 6 years exposure at 18 upland forest sites across Canada. Litter-quality variables used included initial nutrient contents (N, P, S, K, Ca, Mg) and carbon fractions (determined by proximate analysis and C-13 nuclear magnetic resonance spectroscopy). Climate variables used included mean annual temperature; total, summer, and winter precipitation; and potential evaptranspiration. A single-exponential decay model with intercept was fit using the natural logarithm of 0- to 6-year percent MR data (LNMR) for all 198 type by site combinations. Model fit was good for most sites and types (r(2) = 0.64-0.98), although poorest for cold sites with low-quality materials. Multiple regression of model slope (K-f) and intercept (A) terms demonstrated the importance of temperature, summer precipitation, and the acid-unhydrolyzable residue to N ratio (AUR/N) (r(2) = 0.65) for K-f, and winter precipitation and several litter-quality variables including AUR/N for A (r(2) = 0.60). Comparison of observed versus predicted LNMR for the best overall combined models were good (r(2) = 0.75-0.80), although showed some bias, likely because of other site- and type-specific factors as predictions using 198 equations accounted for more variance (r(2) = 0.95) and showed no bias.
This study focused on two questions relevant to ecophysiology: Do distributions of animal species track shifting microclimatic mosaics under field conditions? Do distributions on different levels of spatial resolution (different “scales”) consistently modify a species’ access to heat or humidity? I counted the arthropods on the bark of exposed tree trunks in northern Germany with a 10× lens and investigated how the dominant species (collembolans, psocopterans, isopods, a linyphiid spider, and an oribatid mite) used climatic patterns at various scales. These included mesoclimatic patterns and shifting microclimatic patterns such as microrelief, trunk faces, and trunk/mesoclimate differences. Bias owing to changing frequency of microhabitats, or to redistributions of animals between microhabitats was avoided. I also investigated the effects of climatic patterns on heat and humidity levels at the bark surface. The distributions of all species, except the psocopterans, similarly tracked shifting microclimatic mosaics and mesoclimates. The distributions of most species modified their access to heat or humidity consistently at several mutually independent scales. The remaining species seemed to be restricted in their climate use by sensory or metabolic limitations.
Investigations of the role of microarthropods (Acari and Collembola) in organic matter decomposition and nutrient cycling have shown that they may contribute to primary productivity in nutrient poor conditions. The potential of microarthropods to affect other ecosystem properties, such as above ground plant diversity or succession, lags somewhat. In this contribution we demonstrate: (1) that the effect on the mobilization of nutrients promoted by microarthropods must be measured at the microhabitat scale appropriate to the scale of the faunal activity, and (2) that small changes in the structure of microarthropod assemblages can have significant effects on the local mobilization of nutrients. In the first of two experiments we measured the nutrients leaching from field mesocosms containing litter and mineral soil, with and without fauna. After eight months, the C:N ratios of the litter differed significantly indicating that the fauna were effective in altering the decomposition rate. However, the patterns of release over time and the concentration of the measured nutrients differed little between the two sets of mesocosms. In a second experiment microarthropod assemblages, which differed only slightly, were introduced into laboratory microcosms and the nutrient fluxes were measured over a ten week period. Significant differences were detected in the concentration of nitrogen, K and Mg leached and in CO2 evolved. We suggest that when the potential influence of microarthropods on ecosystem properties is being assessed, specific knowledge of the relevant details of interactions at the smallest scale must be considered. These details can be incorporated or dismissed when interactions on the next level of the ecological hierarchy are examined. Using such analysis we suggest that the creation of soil nutrient hot-spots by microarthropods may have implications for maintaining plant species of lowered competitive ability in a given system.
In this study, we quantify the abundance and composition of the litter fauna in dry and wet tropical forests and north- and south-facing subalpine forests. We used the same litter species contained in litterbags across study sites to standardize for substrate conditions, and a single method of fauna extraction from the litter (Tullgren method). Fauna densities were calculated per gram of dry litter. We found a higher density of total litter fauna and a higher taxonomic diversity in the tropical wet forest (80 individuals and 4 orders per g of dry litter and) as compared to the tropical dry (6 individuals and 1.5 orders per g of dry litter) and the subalpine forests (6–11 individuals and 2 orders per g of dry litter). Oribatid mites (Cryptostigmata) were the most abundant group of fauna across the study sites. The abundance of both micro- and macroinvertebrates was significantly higher in the tropical wet forest than all other sites. Taxonomic diversity (number of orders) was positively correlated with plant litter decomposition across all the sites. We conclude there is a significantly higher density of litter fauna and a greater taxonomic diversity per gram of litter in the tropical wet forest than in the tropical dry and the subalpine forests. Both of these factors can contribute to the differences in litter decomposition rates among the tropical and the subalpine sites.
Although there has been much recent interest in the effect of litter mixing on decomposition processes, much remains unknown about how litter mixing and diversity affects the abundance and diversity of decomposer organisms. We conducted a litter mixing experiment using litterbags in a New Zealand rainforest, in which treatments consisted of litter monocultures of each of 8 forest canopy and understory plant species, as well as mixtures of 2, 4 and 8 species. We found litter mixing to have little effect on net decomposition rates after either 279 or 658 days, and for each species decomposition rates in mixture treatments were the same as in monoculture. Litter species identity had important effects on litter microfauna, mesofauna and macrofauna, with different litter types promoting different subsets of the fauna. Litter mixing had few effects on densities of mesofauna and macrofauna, but did have some important effects on components of the microfauna, notably microbe-feeding and predatory nematodes. At day 279, litter mixing also consistently reduced the ratio of bacterial-feeding to microbe-feeding (bacterial-feeding+fungal-feeding) nematodes, pointing to mixing causing a significant switch from the bacterial-based to the fungal-based energy channel. Litter mixing sometimes influenced the community composition and diversity of nematodes and macrofauna, but effects of litter mixing on diversity were not necessarily positive, and were much weaker than effects of litter species identity on diversity. We conclude that litter mixing effects on the abundance and diversity of decomposer biota, when they occur, are likely to be of secondary and generally minor significance when compared to the effects of litter species identity and composition.
Simple structures aimed at regulating the amount of rain water dropping into the forest floor were installed to determine the impact of rainfall on leaf litter mass loss, respiration rates, microbial biomass C (Cmic) and metabolic quotient (qCO2). The rainfall manipulation treatments were (I) fully covered (100% reduction); (II) partially covered (50% reduction) and (III) control (fully exposed). Using the litterbag technique, the mass losses of covered Quercus serrata, Quercus acutissima, Acer rufinerve and Pinus densiflora leaf litter were reduced (P<0.01) by 19–26% compared to fully exposed litter. A positive linear relationship (r=0.90; P<0.0001) between litter Cmic and mass loss was noted across all litter types and covering regimes. The mass losses in fully exposed litter were attributed to the leaching effect of rainfall coupled with the synergistic actions of microbes and soil fauna, as suggested by their respiration and microbial biomass. In the covered litter, Cmic was generally reduced (P<0.01) while fully and partially exposed litter were comparable (P>0.05). On the other hand, respiration rates and qCO2 were variable and showed no consistent treatment effect except for respiration rates at 3 months. Similarly, soil respiration rates and Cmic were not consistently affected by cover treatments. Evidently, the zero-rainfall condition negatively affected some biological processes in the litter layer but sporadically affected soil processes. The absence of rainfall, even if the soil moisture content was maintained, could affect organic matter turnover in the forest floor.
Forest canopies support diverse assemblages of free-living mites. Recent studies suggest mite species complementarity between canopy and terrestrial soils is as high as 80–90%. However, confounding variation in habitat quality and resource patchiness between ground and canopy has not been controlled in previous comparative studies. We used experimental litter bags with standardized microhabitat structure and resource quality to contrast the colonization dynamics of 129 mite species utilizing needle accumulations on the ground vs in the canopy of Abies amabilis trees in a temperate montane forest in Canada. Mite abundance and species richness per litter bag were five to eight times greater on the ground than in the canopy, and composition differed markedly at family-, genus-, and species-level. Seventy-seven species (57%) were restricted to either ground or canopy litter bags, but many of these species were rare (n
The relative contribution of different types of litter to the maintenance of soil organic matter and nitrogen levels cannot be determined from standard litter bag disappearance studies. By coupling measurements of weight loss with nitrogen dynamics and presenting results in a new format, estimates of both state of decay and percentage of material eventually transferred to lower soil horizons can be obtained. -Authors
Fine litter deposition and decomposition within the upper tree canopy was measured in a neotropical cloud forest to determine the potential nutrient input to epiphyte communities from intercepted tree litterfall. A comparable amount of fine litter passed through the canopy (752 g@?m^-^2@?yr^-^1) as arrived on the forest floor (820 g@?m^-^2@?yr^-^1), but <1% of the biomass and nutrients of this @'gross litterfall@' was retained within the upper tree canopy. The standing crop of litter in the canopy (@?170 g/m^2 of branch surface area, 8.8 g/m^2 of ground area) is equivalent to only 1% of the standing crop of litter on the forest floor. Measurements of leaf litter attrition (whole leaf loss from branches due to wind and other disturbances) with marked leaves documented that 70% of leaves deposited on branches are lost in the first 2 wk and nearly all are gone in 16 wk. Certain branch characteristics (branch angle, number of epiphyte stems and clumps) appear to affect the amount of litter retained at particular microsites. Decomposition of tethered, dead leaves within the canopy over a 12-mo period was half that of leaves on the forest floor (canopy litter turnover time = 2.8 yr). Assuming that litter accumulation within the canopy is at steady state, the biomass of fine litter retained and decomposed within the canopy was calculated as only 2.0 g@?m^-^2@?yr^-^1 and < 0.02 g@?m^-^2@?yr^-^1 for all nutrients. Nutrient replenishment of epiphyte communities appears to be decoupled from the litterfall pathway, as input from litterfall retained within the canopy is small relative to epiphyte productivity and nutrient requirements reported in other studies.
Litterbags and arthropod defaunation techniques were used to evaluate the effects of soil-litter fauna on loss of dry matter and nutrient elements from native litter in arctic tundra. A control and a naphthalene-treated plot were established in each of three microhabitats. Faunal populations, litter dry mass and% N, and the concentration of Ca, Na, Mg, Mn, P, Zn, and K in the litter were measured from each litterbag. Litterbags were collected at 10-d intervals during the 1974 nonfrozen season and twice in 1975. Litter mass and nutrient loss differed among habitats and exhibited differing responses to defaunation, as did dry mass loss. Generally greater dry mass loss and less nutrient loss occurred from the litter in the control than in the corresponding defaunated plot. Nutrient loss was greater in plots that are subjected to natural periodic flooding than in plots never flooded. Log"e regression lines of percent mass loss vs. days are reported for each plot on a calendar year and a nonfrozen season basis. Results of this study are compared with results from decomposition studies in other arctic and temperate systems.
Within the canopy of old-growth redwood (Sequoia sempervirens (D. Don) Endl.) forests, accumulations of plant debris in crotches and on massive limbs serve as parent materials for ''arboreal soils'' up to 1 m thick and over 50m above the forest floor. These soils are important habitats and water sources for desiccation-sensitive organisms in the forest canopy ecosystem. We investigated two of these arboreal soils to better understand how they form and function. The primary vascular epiphyte growing in these soils is leather-leaf fern (Polypodium scouleri). Fern biomass and redwood leaves and bark are the main parent materials of the soils, which are entirely organic. The soils have distinct horizons and soil structure, and have been changed from their initial parent materials as a result of additions, losses, and transforma- tions of organic matter. They are classified as Typic Udifolists. The soils become more decomposed with depth as fibrous components transition to sapric materials. They have low bulk densities (0.07- 0.16 g cm 23 ) and lose most of their water at relatively high matric potentials. Field water contents and potentials of the arboreal soil materials taken near the end of the dry season indicate that water remains available for uptake by ferns. High base saturation values (.55%) suggest that nutrients are available for plant uptake. The soils are extremely acidic, with pH values around 3.0 in 0.01 M CaCl2. Decomposition may be hindered by the low soil pH and by relatively low soil moisture contents in surface horizons during the dry season.
Microarthropod abundance, oribatid mite species richness and community composition were assessed in the high canopy (ca. 35 m) of an ancient temperate rainforest and compared with microarthropod communities of the forest floor. Microarthropods were extracted from 72 core samples of suspended soils and 72 core samples from forest floors associated with six western redcedar trees in the Walbran Valley on the southwest coast of Vancouver Island, Canada. Total microarthropod abundances, mesostigmatid and astigmatid mites, Collembola and other microarthropod abundances were significantly greater in forest floors compared to canopy habitats. Oribatid and prostigmatid mite abundance were not significantly different between habitats. The relative abundances of all microarthropod groups considered in this study differed significantly between habitats. Eighty-eight species of oribatid mites were identified from the study area. Eighteen of the 53 species observed in suspended soils were unique to the canopy. Cluster analysis indicates that the arboreal oribatid mite community is distinct and not a taxonomic subset of the forest floor assemblage, however, canopy oribatid mite communities are more heterogeneous in species composition than in the forest floor.
Succession of microarthropods during the decomposition of organic matter is an important concept in soil biology. However, few studies have tested whether the pattern of microarthropod colonisation during decomposition is independent of season. We investigated the pattern of colonisation and dominance of microarthropods on decomposing organic matter placed at two different times. Litterbags containing canola leaf or stem material were placed on the soil surface of a Western Australian agricultural field in July and September 1999. They were collected weekly to fortnightly until November. A final set of bags was collected in May 2000. Mass loss and nutrient contents (C, N, Ca, K, P and S) were measured at each sample time. Microarthropods were sorted to order and the mites to species level. Nematode abundance was determined at each sample time. Mass loss of the leaf and stem material was similar between the two placement times (≅33% and 15% ash-free dry mass lost over 33 days from leaf and stem material, respectively), although the dynamics of nutrient loss for some elements was different between the two placements. However, over the dry summer, material placed in September continued to lose nutrients whilst there was little additional loss from the material placed in July. A similar pattern of dominance of microarthropod and mite species was found on the leaf and stem material placed in July with the succession of dominant animals more rapid on the stem material. Nematode abundance appeared to increase as populations of microarthropods declined over time. Populations of microarthropods on the material placed in the September samples never achieved similar levels of abundance to that of the July samples, and the dominant fauna groups were dissimilar to those in the July samples for the same degree of decomposition. Our data indicate that the early phase of surface litter decomposition is not a successional process in terms of the microarthropod community irrespective of season and, that abiotic factors are more likely to be determining nutrient loss from organic matter within particular seasons.
Accumulations of organic material can be found in the crowns of trees in tropical wet forests. We investigated moisture and temperature patterns of dead organic matter in the canopy and of soil in the upper horizons of the forest floor over a 42-month period. Temperatures of the canopy material and forest floor soil fluctuated throughout the year (range = 11.5"C to 21.OoC), but remained within an average of 1°C of each other. Both canopy material and forest floor soils were moist throughout the wet and misty seasons (over 70% water content). Although canopy organic substrate experienced periods of rapid and severe dehydration during the dry season (20%-40% water content), forest floor soils remained at a consistently high water content (60%-70%). The more extreme and fluctuating moisture conditions of canopy organic material may be important in determining the distribution and activity of epiphytic plants and associated canopy organisms.
Oribatid mites (Acari: Oribatidae) are the most diverse arthropod group in forest litter and soil, and they make significant contributions to decomposition as microbial grazers and saprophages. As is true for all the hyperdiverse soil taxa, the determinants of their diversity and species composition are virtually unexplored. This experiment tests whether heterogeneity of the litter habitat is a determinant of their local diversity, and whether litter composition is a determinant of their species composition. At a single site of temperate deciduous forest at the Coweeta Hydrological Laboratory in the mountains of North Carolina, USA, natural litterfall was excluded from a series of 42 1-m2 plots and, for three consecutive years, replaced with treatment litters that varied in their composition and complexity. Plots of pure yellow birch (Betula alleghaniensis), sugar maple (Acer saccharum), and red oak (Quercus rubra) litter comprised the monotypic or simple litter treatments. Two complex litters included a mixture of these three litter species and a mixture of seven litter species with pieces of small woody debris. Monotypic litters developed profiles of reduced thickness that contained lower numbers of invading roots and less humic and arthropod fecal material. Over 3 yr, oribatid abundance and richness declined substantially and to a similar degree in all simple litter treatments, though the dominant species, Oppiella nova, was unaffected by litter simplification. Similarity of species composition increased markedly among replicates within each litter treatment for two sectors of the assemblage: the large, litter-dwelling species and the endophagous and wood-associated species. Species composition among small litter-dwellers was unresponsive to litter type. Several characteristics of monotypic-litter habitats potentially contributed to the erosion of the oribatid assemblage. Loss of structure in monotypic litter likely led to reduced and less hospitable physical living space. It appeared to reduce recruitment of roots and retention of humic and fecal material in the litter layer. Each monotypic litter contained only a subset of the structural microhabitats that serve as refugia for eggs and juveniles. Finally, the synchronized decomposition of uniform substrates could have led to a 'boom-bust' economy in microbial resources that was unfavorable to oribatid mites and their conservative life histories.
A recently described soil testing procedure for simultaneous estimation of plant‐available phosphorus (P) and potassium (K) in soil uses an aqueous solution containing ammonium fluoride, ammonium acetate, and acetic acid (the “modified Kelowna”; or KM extract). Before adopting a KM method at our laboratory (in 1988) for routine soil testing, we compared its ability to predict crop response to phosphate fertilizer using data from field sites on a wide range of soils in Alberta and Saskatchewan with that of the Olsen and the Miller‐Axley (Bray‐type) soil testing methods. All three methods were unable to predict with great accuracy actual optimum rates of phosphate fertilizer in these trials, but they predicted the likely crop yield response to phosphate reasonably well. The main advantages of the KM test over the others are its analytical convenience and its applicability to calcareous soils.
The relative contribution of different types of litter to the maintenance of soil organic matter and nitrogen levels cannot be determined from standard litter bag disappearance studies. By coupling measurements of weight loss with nitrogen dynamics and presenting results in a new format, estimates of both state of decay and percentage of material eventually transferred to lower soil horizons can be obtained.
Microarthropods have a variable but generally significant effect on litter disappearance and therefore on detrital standing crops. An average increase in litter decomposition rates of 23% was noted for 15 studies that ranged from 9-30 months in duration. Increased mineralization of N, P and K was seen in only about half of those studies reporting microarthropod effects on nutrient dynamics. Mass loss is more affected than are nutrients owing to stimulation of microbial respiration by microarthropods. This respiration results in carbon mineralization but converts other elements into microbial tissues, most of which is recycled within the detritus. Mineralization of N, P and cations will probably increase in older litter as a result of microarthropod feeding activities. Directions for future research are indicated.-from Author
Many chemical reactions at the Earth's surface are influenced by biota. Ecosystem ecologists study the flow of matter and energy in ecosystems com-posed of organisms and their abiotic environments. The study of ecosystem ecology can blur distinc-tions between 'basic' research and environmental management. How does our behavior (including ur-ban development and land-use, water consumption, pollution) influence the movement of energy, water, and elements at local, regional, national or global scales? Will perturbations to chemical and energy cycles alter existing controls on ecosystem pro-cesses, and can we learn enough about them for effective regulation? Plants are critical in regulating biogeochemical cycles. Their growth controls the exchange of gases that support life in our current biosphere, and af-fects soil development. As primary producers, they influence the distribution of energy for higher tro-phic levels. Understanding how plants influence ecosystem processes requires a multidisciplinary approach drawing on plant physiology and bio-chemistry, community ecology, and biogeochem-istry. Due to their unique physiology and ecology, bryophytes differ from vascular plants in influenc-ing cycles of elements, energy, and water. For ex-ample, bryophytes have evolved an effective water relation system. Poikilohydry and desiccation tol-erance allow bryophytes to tolerate longer periods of water stress than vascular plants, and to recover quickly with rehydration. With poorly developed conduction systems, water and solutes are taken up over the entire plant surface. Lack of both game-tophyte stomata and effective cuticles in many spe-cies allows free exchange of solutions and gases across cell surfaces. Thus bryophytes often serve as effective traps for water and nutrients. This also makes them more sensitive to atmospheric chemi-cal deposition than vascular plants. Bryophytes also can tolerate a wide range of temperatures and are found in almost all terrestrial and aquatic environments, including harsh Antarc-tic environments where vascular plant cover is low (cf. Fogg 1998; Seppelt 1995). Without roots, bryo-phytes can colonize hard substrates like rock and wood that are poor habitat for vascular species. Bryophytes stabilize soils and prevent the loss of soil and nutrients via erosion, particularly on sand dunes (Martinez & Maun 1999) and in cryptogamic soil crusts (Eldridge 1999; Evans & Johansen 1999). Cation exchange on Sphagnum cell walls re-leases protons, generating acidity that may inhibit plant and microbial growth (Clymo 1963; Craigie & Maass 1966; Spearing 1972). Finally, bryophytes influence ecosystem succession (Brock & Bregman 1989) through terrestrialization of water bodies, de-position of benthic organic matter or paludification of upland systems. Bryophyte colonization often precedes the establishment of tree surfaces by other canopy-dwelling plants (Nadkarni et al. 2000). Due to their physiology and life history traits, bryophytes influence ecosystem functions by pro-ducing organic matter, stabilizing soils or debris, trapping sediments and water, and providing food and habitat for algae, fungi, invertebrates, and am-phibians. In this review, my objectives are to high-light several mechanisms by which bryophytes in-fluence carbon (C) and nitrogen (N) cycles within and fluxes from ecosystems. As such, I will focus on how bryophytes fix, intercept, transform, and/or release C and N. My goals are to 1) introduce im-portant processes controlling inputs and outputs of C and N in both terrestrial and aquatic ecosystems, 2) review work on the growth, decomposition, and leaching of bryophyte material, as well as biotic and abiotic controls on these mechanisms, and 3) suggest areas for future research that would ad-vance our understanding of bryophytes in biogeo-chemical cycling.
The ecological implications of the conversion of old-growth temperate rainforests to managed forests have generated much discussion worldwide. This paper examines the effects of such a conversion on different aspects of the biodiversity of the soil collembolan fauna, and attempts to determine the time that will be required for the collembolan fauna to approach the abundance and community structure seen in old-growth forests. The study also investigates the potential of using different measures of species diversity and community structure as indicators of old-growth conditions in forest soils. The study was carried out in three chronosequence sites in Douglas-fir dominated stands on the dry leeward eastern side of Vancouver Island, BC, Canada. Each of the three sites contained stands representing four stages of stand development: regeneration (7–9 years), immature (35–46 years), mature (80–102 years) and old-growth (>248 years). The Collembola were extracted from litterbags containing needle litter or wood chips, and from the forest floor (LFH) layer in the late autumn of four successive years.
Aim This study investigates the species–area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes.
Addition of single species of soil animals to animal-free microcosms often increases total heterotrophic respiration, but sometimes additions of microarthropods have been reported not to increase or even decrease CO2 evolution rates. Most studies indicate that addition of soil animals increases net N mineralisation. In a study with F/H layer materials from a spruce stand in central Sweden kept at two temperatures (5 and 15C) and three moisture levels (15, 30 and 60% of WHC), addition of a mixed fauna of soil arthropods, mainly microarthropods, could not be shown to change the CO2 evolution rates in comparison with materials where arthropods were absent. However, addition of the arthropods significantly increased net N mineralisation for each of the temperature and moisture combinations. The increase due to the arthropods was dependent on soil temperature but not on soil moisture. Because the total net N mineralisation decreased with decreasing soil moisture, the soil arthropods had a much larger relative effect on net N mineralisation under dry than under moist conditions. It is concluded that soil arthropods are important in maintaining net N mineralisation under dry conditions when the microflora is largely inactive. The microbial/faunal release of mineral N is discussed in relation to the CN of the substrate.
Spruce needles of different age, litter materials and soil samples from the L-, O-and A-horizons of a mor profile were analysed by temperature-programmed pyrolysis (Py) in combination with field ionization mass spectrometry (FIMS). The integrated Py-FI mass spectra give characteristic fingerprints of the biomaterials investigated. The application of principal component analysis to the mass spectral data results in a clear discrimination and classification of the samples reflecting the chemical modifications and transformations of organic matter by biochemical and biogeochemical processes. The chemical compositions are determined by processes such as enrichment and/or translocation of plant constituents (e.g. carbohydrates, lignin, lipids, suberin, and aliphatic polymers) during maturation and senescence of needles; amendment of new components; decomposition; selective preservation and humification processes in the soil environment.
During needle maturation, major chemical changes include the decrease of carbohydrate content, condensation of lignin, and crosslinking of waxes. Senescent needles are characterized by lower contents of carbohydrates and lower yields of monomeric pyrolysis products from lignin. The contribution of different litter materials to the humus layer can be estimated by differences in chemical composition. During litter decomposition and humification on the forest floor, carbohydrate content decreases rapidly. The lignin content remains almost constant but some subunits are continuously oxidized. Wax material accumulates until the mechnical disintegration of the needle occurs. In the O-horizons polymeric aliphatic materials are enriched in humified plant remains. A constant increase of aryl-alkyl esters from suberin in the O-horizons is due to both root input and selective preservation. In general, mainly aliphatic polymers and aryl-alkyl esters accumulate during the genesis of mor profiles under conifers.
This microcosm study is concerned with understanding those factors which regulate ecosystem processes of nutrient cycling and plant productivity in a montane grassland ecosystem. We examined the effects of different groups of soil fauna, namely bacterial-feeding nematodes and Collembola, on nutrient mineralization (N and P) in an acid, organic soil taken from a montane grassland in the Peak District National Park, United Kingdom. We also examined whether faunal influences on nutrient release, a measure of nutrient mineralization, resulted in changes in nutrient uptake and biomass production of an indigenous montane grass species (Nardus stricta (L.)). We found that in the presence of Collembola, and when nematodes and Collembola were combined, N mineralization, nutrient leaching and shoot N contents of N. stricta was significantly increased relative to a defaunated control. We also found that net P mineralization and leaching increased (although not significantly) in the presence of both nematodes and Collembola, resulting in a significant increase in shoot P content of N. stricta. The presence of nematodes alone, which were largely bacterial-feeders, had no effect on the mineralization of N or P, or shoot nutrient content. We suggest that differences in the effect of faunal treatments on nutrient mineralization are related to the feeding strategies of the added fauna, and to their consequent effect on the size of the soil microbial biomass. The treatments that increased N mineralization and plant nutrient content (N and P) also significantly reduced plant growth (shoot and root). We suggest that high NH4+–N concentrations in the soil solution of Collembola treatments inhibited the growth of N. stricta and that the growth of other grassland species may benefit from this improvement in nutrient availability.
Japanese cedar (Cryptomeria japonica D. Don) plantations tend to have poor soil–litter conditions, which may influence the activity and composition of microbial and faunal communities in the soil–litter subsystems. The effects of microarthropods (Acarina and Collembola) on the decomposition processes of C. japonica needle litter were examined with litter mesh boxes over a 2-year period. After 5 months, the mass loss of needle litter in the fauna-excluded boxes (mesh size 25 μm) was significantly higher than that in the control boxes (mesh size 1 mm) but after 10 months, it was significantly lower than that in the control boxes. The density of total microarthropods, 77% of which were collembolans and oribatid mites (Cryptostigmata), was strongly correlated with the mass loss rate. The C/N ratios of the litter in the control treatments were significantly lower than those in the fauna-excluded treatments after 10 months. However, the presence of microarthropods in the boxes had no significant effect on the amounts of nitrogen immobilized in the litter. Annual decomposition rates (k) of needle litter were 0.377 in the control treatment and 0.298 in the fauna-excluded treatment. Based on Seastedt's equation (1984), microarthropods increased the decomposition rate of needle litter (kfauna/ktotal) by 21%. Our results indicate that microarthropods accelerate the overall decomposition rate of C. japonica needle litter, despite inhibiting decomposition temporarily.
The effect of three collembolan species on decomposition and N mobilization was studied in a Pinus nigra plantation, using field enclosures and by trenching tree roots. The fauna were added to defaunated organic material. Estimates were made of weight and N losses from fresh litter, fragmented litter and humus after 7 months exposure. N mobilization was also measured as leachable mineral N using suction cup lysimcters. and was found to be dominated by NO3−-N. In the presence of the surface dwelling Orcheselln cincta (L.) a net loss of 310 mmol m−2 of total N in humus was observed, as opposed to a small gain of 76 mmol N m−2 in the control. Tomocerus minor (Lubbock) induced a nearly two-fold increase in the mobilization of NO3−-N to the leachate compared to Isotoma nolabilis Schäffer. possibly as a consequence of differences in grazing saprotrophic fungi. The influence of I. notabilis on the experimental systems differed from the effects of the other Collembola in effecting an increased mass loss of humus material. Tree roots suppressed fragmented litter decomposition significantly by 2.0%. and had considerable effect on N dynamics. In the presence of roots, leachable quantities of NO3−-N were reduced to half the amounts that were collected in their absence. The amount of total-N of fragmented litter was nearly unchanged in non-rooted plots, but was reduced at a rale of 274 mmol m−2 after 7 months. It was concluded that C and N mineralization in soils is influenced by the ecological characteristics of the dominant species and is not simply a function of trophic group or biomass.