Litter Macrofauna Research Articles

Stages of Restoration of Components of Post-Agrogenic Pine Forest Ecosystems at the National Park “Smolensk Lakeland”

Rural depopulation in Russia was accompanied by the abandonment of arable lands and natural reforestation. The aim of the work was to study soils and phytocenoses of six stages of pine forest restoration on rocks with coarse granulometric composition in the north-west of Smolensk region. The research was carried out at 18 key sites, characterizing 6 stages in triplicates. Under agrocenoses and one-year-old fallow lands we found agrozemes (Arenosols (Aric)) with a thick arable layer and a minimum abundance and biomass of macrofauna, represented mainly by phytophages and saprophages. At the 2nd stage of fallow meadows, grey-humus soils (Arenosols) and sod-podzols postagrogenic (Entic Podzols) were found with unchanged morphological properties in comparison with the first stage. Here, the biomass of macrofauna is maximal due to intensive invasion of open biotopes by insects. Young (up to 30 years old) pine forests grew on similar to the Stage 2 regraded soils. During 10 years of a forest growth, litter and protohumus regrading horizons were formed. In middle-aged (70–80 years old) pine forests on sod-podburs post-agrogenic regraded (Entic Podzols), signs of an eluvial process are manifested. Macrofauna is characterized by a decrease in the biomass of a litter population. In forests older than 80 years, decay of pine stands with the formation of complex spruce forests have begun. In soils, even lower boundary of old-fallow horizon disappears without podzolic horizon formation. Here, the maximum biomass of litter macrofauna is revealed. The final stage is shrubby (lingonberry)-green-moss pine forests older than 90 years growing on podzols (Albic Podzols) with remains of old-fallow horizon. Among macrofauna, litter macrofauna prevail in terms of a biomass, but the biomass is lower than in the previous stage. Due to the different degree of morphological manifestation of the alfegumus process, the fifth and sixth stages can be considered as variants of the development of post-agrogenic soils under pine forests.

Litter-dwelling invertebrates in natural and plantation forests in the southern Carpathians, Romania

Forest plantations usually have a poorer fauna than native forests of the same region. Exceptions seem to appear in colder areas of Europe with few native forests. The Jiu Gorge National Park (JGNP) is situated in the Southern Romanian Carpathians, where numerous native, especially beech, forests are present. However, in the southern part of JGNP there are plantations with non-native species, like pine or black locust, where previous studies had reported a poor fauna. Based on this information, we supposed that this fauna poverty in plantations will be obvious also in the case of the litter macrofauna. This was verified by analyzing the litter macrofauna from 15 forests in the JGNP (10 natural forests and five forest plantations). We collected 12,950 individuals belonging to 28 invertebrate groups. The highest number of taxa was registered in the sessile oak forest, while the highest individual number and taxa diversity was observed in two beech forests. In the beech and birch reforestation areas the fauna was poorer than in old mature forests of the same tree species. In contrast to native forests, the fauna in plantations was much poorer, especially in the pine plantations. Detritiphagous taxa were the most affected by factors of the plantations. In the plantations, more mobile groups with various trophic regimes prevail. The plantations that are present in the southern areas of JGNP, replaced the original sessile oak forests, compared to which they have a much poorer fauna. Forest plantations from JGNP have low value for biodiversity, compared to the northern European areas where natural forests became very rare and the fauna is recent. JGNP is not in the same situation, having extended native forests, which are present in the area since the glacial periods. Therefore, these forests shelter the native fauna of the region. There are few plantations, present only in the disturbed part of JGNP, but even there they have only a very low importance for biodiversity. The data from JGNP confirms the fact that zones with high biodiversity and native forests should be conserved.
 Key words: Carpathians, beech, forest plantations, past, native, invertebrates, leaf litter, forestry.

Tree canopy affects soil macrofauna spatial patterns on broad- and meso-scale levels in an Eastern European poplar-willow forest in the floodplain of the River Dnipro

Abstract This paper tested the hypothesis that the placement of trees in the floodplain ecosystem leads to multiscale spatial structuring and plays an important role in formation of the spatial patterns of the soil macrofauna. The research polygon was laid in an Eastern European poplar-willow forest in the floodplain of the River Dnipro. The litter macrofauna was manually collected from the soil samples. The distances of the sampling locations from the nearest individual of each tree species were applied to obtain a measure of the overstorey spatial structure. The pure effect of tree structured space on the soil animal community was presented by the broad-scale and meso-scale components. The soil animal community demonstrated patterns varying in tree structured space. The tree induced spatial heterogeneity was revealed to effect on the vertical stratification of the soil animal community. The complex nature of the soil animal community variability depending on the distance from trees was depended on the interaction of tree species in their effects on soil animals. The importance of the spatial structures that interact with soil, plants and tree factors in shaping soil macrofauna communities was shown.

Influence of the herbaceous layer and litter depth on the spatial distribution of litter macrofauna in a forest plantation

The litter invertebrate community consists of species from different size, trophic and taxonomic groups. The distribution of the animal population of the litter horizon depends upon many factors, especially the content of the phytocoenosis, the projective herbaceous plant cover, moisture, litter thickness and the soil texture. This article analyses the variability of the main characteristics of litter invertebrate communities (total number, number of species, diversity according to the Shannon–Wiener and Pielou indices) on plots with different herbaceous plant composition and cover in plantations of Robinia pseudoacacia L. in the South steppe zone of Ukraine (territory of the “Tiligulsky” Regional Landscape Park). The taxonomic structure of the litter communities in the Robinia plantation was dominated by predatory groups of invertebrates (Carabidae, Aranea, Formicidae). The abundance of Julidae, Isopoda, Silphidae and Staphylinidae was relatively low. The studied forest plots were characterized by the simplified size structure of the litter macrofauna. The absence of species with body length of 16–20 mm and length over 20 mm indicates damage to the most significant trophic chains. The forest belt studied is in a highly disturbed condition, the plots being dominated by steppe species of herbaceous plants. The analyzed factors (diversity and extent of cover of herbaceous plants) do not determine the structure of the litter macrofauna community but affect it indirectly: a slight increase in the total number of invertebrates was observed in areas with minimal and maximum number of species of herbaceous plants. The relationship between the abundance of invertebrates and the percentage of herbaceous plant cover is manifested insignificantly. We noted a tendency for the number of invertebrate species to decrease along the gradient of herbaceous plant cover due to the concentration of dominant predatory species which exterminate other trophic groups of macrofauna.

Structure of litter macrofauna communities in poplar plantations in an urban ecosystem in Ukraine

The litter macrofauna of 8 plantations of Populus italica (Du Roi) Moench, P. deltoides Marsh. and P. alba L. was studied in the city of Dnipro. The invertebrates were taken by manual sifting of litter from experimental plots of 8 m 2 . The total number of litter macrofauna in the poplar plantations varied from 8 to 187 specimen/m 2 , on average 53 specimen/m 2 . The greatest variety of species was obtained from a white poplar plantation with common hop and an elm-poplar plantation with bare soil and Amorpha fruticosa L. bushes (15 and 9 species correspondingly). The ma ximum readings on the Shannon–Weaver diversity index come from the abovementioned areas (3.2 and 2.9 bits respectively). The highest number of zoophages (40%) was obtained from the white poplar plantation with common hop. There was great consistency in the species composition across the plots, with the same 60 species (more than 50% of the total number of species of litter macrofauna recorded in the study) being found in 7 out of the 8 study plots. The share of species rare for any given ecosystem exceeded 10% in only 2 out of the 8 plantations studied. The dominant group in the size structure of the litter macrofauna of the poplar plantations (44–96%) was invertebrates of 4–7 mm length. In 5 out of 8 poplar plantations no species over 15 mm in length were found. This indicates the degraded size structures of the litter macrofauna communities. In taxonomic structure the dominant groups were Formicidae, Pulmonata, Porcellionidae, Lygaeidae, Julidae, Silphidae, Araneae, Carabidae, Staphylinidae. The results obtained indicate the low variety and degradation of the trophic and size structure of the litter macrofauna of these urban poplar plantations, which are subject to lack of moisture.

The influence of moisture conditions on the structure of litter invertebrate communities in shelterbelt and plantation forests in southern Ukraine

Context: The distribution of different size groups of litter invertebrates in varying gradations of moisture conditions is therefore of interest for a better understanding of the coordination of the components of the ecological community.Objectives: The aim of this work is to evaluate the effect of long-term average moisture conditions on the basic characteristics of the litter macrofauna of plantations in southern Ukraine.Materials and Methods: Invertebrates were collected with pitfall traps annually throughout the vegetational seasons of 2001–2013 in 176 plantation sites.Results: The average number and the quantity of invertebrate species in the litter decreases with the increase of the moisture content. The indices of biological diversity are maximal in xeromesophilous and mesophilous moisture conditions. Phytophages are distributed evenly in the litter of forest plantations. The number of saprophages is maximal in xeromesophilous (36%) and minimal – in hygromesophilous (3%) conditions. Zoophages increase in relative abundance from 14% in mesoxerophilous to 63% in hygromesophilous conditions. The abundance of polyphages does not change significantly in varying gradations of moisture (26–46%). The size structure of communities is dominated by the group ranging from 4 to 7 mm in body length (31–52%). The relative abundance of the size group exceeding 20 mm in body length reaches its maximum (16%) in mesoxerophilous conditions, and decreases (4–10%) in other gradations of moisture. The share of the size group of <4 mm is maximal (28%) in mesophilous conditions. Carabidae, Formicidae and Lycosidae form part of the dominant families in all four of the moisture gradations of artificial forests studied, while other families represent more than 3% only in plantations belonging to three gradations of moisture.Conclusion: Litter moisture is a limiting factor for invertebrate existence in the extreme conditions of forest ecosystems, especially in the south of the steppe zone of Ukraine.J. bio-sci. 22: 77-88, 2014

Effect of canopy density on litter invertebrate community structure in pine forests

Abstract We investigated the structure of the litter invertebrate community in 141 pine (Pinus sylvestris Linnaeus, 1753) forest sites with five variants of canopy density (30-44, 45-59, 60-74, 75-89 and 90-100%) in the steppe zone of Ukraine. The total number of litter macrofauna specimens collected at each site decreased from an average of 84/100 trap-days in the sparsest stands (30-40% density) to 4-39 specimens/100 trap-days in the forests with a denser canopy. The number of macrofauna species caught in the pitfall traps does not vary significantly with different degrees of canopy density. The Shannon-Weaver and Pielou diversity indexes show increases corresponding to increasing stages of canopy density. The average share of phytophages in the trophic structure of the litter macrofauna does not vary with canopy density. The relative number of saprophages decreases from 54% in the forests with the sparsest canopy to 11-13% in the forests with denser canopies. The relative number of saprophages in pine forests (22%) is lower than that in deciduous forests (40%). The share of zoophages in the trophic structure of the litter macrofauna increases significantly with the increase in the pine forest canopy density (from 21% in the sparsest plots to 59% in the densest). The relative number of polyphages is highest (47-65%) when the canopy density is 45-89%. At canopy densities below or above this range, the share of polyphages in the community decreases to 20 and 24%, respectively. Regardless of canopy density, Formicidae and Lycosidae invariably rank amongst the first three dominant families. Nine families of invertebrates dominate in the pine forest stands with the highest density (90-100%), and 5-7 families dominate in the stands with lower density. For the pine forest litter macrofauna, we have observed an extreme simplification of the community size structure compared with natural and planted deciduous forests of the steppe zone of Ukraine.

Influence of litter thickness on the structure of litter macrofauna of deciduous forests of Ukraine’s steppe zone

The litter in a forest ecosystem acts as a trophic substrate, and at the same time it is the environment for litter invertebrates. But despite this fact, there has been very little research conducted on the influence of litter thickness on the structure of litter macrofauna. The litter of steppe forests contains most types of integrated communities of forest ecosystems. This means that its thickness cannot avoid playing a significant role in the functioning of the ecosystem. Following to the standard methodologies, Invertebrates were collected using pit-fall traps in deciduous forests of Nikolaev, Zaporizhzhya, Dnipropetrovsk, Donetsk and Kharkiv oblasts, which are characterized by different types of geomorphological profile, different moisture conditions, soil salinity, tree crown and herbaceous vegetation density, soil texture and other factors. The total number of macrofauna increases in conditions where litter thickness exceeds40 mmin comparison with forest ecosystems with fragmented and average capacity litter. The number of litter macrofauna species also increases from 11–23 to 38 species on average when litter thickness increases to more than40 mm. The Shannon and Pielou diversity indexes show no definite tendencies to change in relation to changing degrees of litter thickness. At sites of greater thickness of the litter layer, the corresponding increase in the absolute number of litter mesofauna invertebrates is mostly due to saprophages, and the increase the number of species – due to zoophages. The optimum structure of domination was observed at sites with maximum thickness of litter. The proportion of large species shows no statistically significant change in relation to variations in litter thickness. The qualitative compound of the fauna at sites with thick litter changes mainly due to an increase in the number of Carabidae species.

Вплив зімкненості крон дерев і покриття трав’янистих рослин на структуру підстилкової мезофауни широколистяних лісів степової зони України

Здійснено аналіз підстилкової мезофауни широколистяних лісів на території Дніпропетровської, Запорізької, Миколаївської, Донецької областей України у 339 природних лісових екосистемах у 2001–2014 рр. Зімкненість крон дерев достовірно не впливає на чисельність підстилкової мезофауни та кількість видів безхребетних у підстилці. Індекси різноманіття Шеннона та Пілоу мають тенденцію до підвищення у градієнті зімкненості крон дерев (від менше 50% до 90–100%). Відносна чисельність сапрофагів і зоофагів мінімальна (медіана 18% та 3%) у лісових екосистемах із розрідженим наметом, має тенденцію до зростання у лісах із зім­кненим деревостаном (40% та 18%). Відносна чисельність поліфагів у мезофауні, навпаки, в таких умовах зменшується з 82% до 27%. Кількість видів кожної трофічної групи достовірно не змінюється у градієнті зімкненості крон дерев у широколистяних лісах степової зони. В умовах 70–79% зімкненості крон дерев розмірна структура підстилкової мезофауни наближається до оптимальної. Відносна чисельність мурах у підстилковій мезофауні максимальна (73%) у розріджених деревостанах (менше 49%), відносна частка Isopoda максимальна (медіана 40%) також в умовах розрідженого деревного намету (50–59%). У зімкнених деревостанах таксономічна структура на рівні рядів і родин стає більш вирівняною, у ній зникають домінанти, з відносною чисельністю понад 15%. Відносна чисельність більшості домінантних родин і рядів у градієнті зімкненості крон дерев достовірно не змінюється. Вплив покриття трав’яного ярусу менший, ніж деревного ярусу. Чисельність мезофауни підстилки широколистяних лісів максимальна у двох крайніх варіантах розвитку трав’яного ярусу: фрагментарний трав’яний ярус (покриття менше 15%) та щільний травостій (покритя 90–100%). Мінімальна чисельність підстилкової мезофауни реєструється в умовах середнього покриття трав’яними рослинами (45–59%). Кількість видів, індекси різноманіття Шеннона та Пілоу достовірно не змінюються у градієнті покриття ґрунту трав’яними рослинами у широколистяних степових лісах. Кількість видів фітофагів зростає в лісових екосистемах із середніми значеннями покриття трав’янистих рослин, а сапрофагів, зоофагів і поліфагів достовірно не змінюється. Структура домінування підстилкової мезофауни найбільшою мірою трансформована у крайніх варіантах розвитку трав’яного ярусу: за фрагментарного трав’яного покриву (менше 15%) та суцільного розвитку трав’яного ярусу (90–100%). Медіана кількості видів турунів максимальна для 15–29% покриття трав’яного ярусу. Відносна чисельність Carabidae у проаналізованих градаціях покриття трав’яної рослинності достовірно не змінюється. Медіана відносної чисельності Formicidae максимальна в умовах 60–74% покриття трав’яної рослинності, Isopoda – за 15–59% покриття трав’яного ярусу.

Influence of moisture conditions and mineralization of soil solution on structure of litter macrofauna of the deciduous forests of Ukraine steppe zone

The accounting of litter mesofauna was carried out in the territory of Dnipropetrovsk, Zaporizhzhya, Nikolaev,Donetsk regions of Ukrainein the natural forest ecosystems in 2001–2014. 339 forest ecosystems were surveyed; xeromesophilic conditions of moistening were characteristic for 47 trial sites, mesophilic conditions – for 99 sites, hygro-mesophilic conditions – for 50 sites, meso-hygrophilic conditions – for 89 sites, hygrophilic conditions – for 54 sites; trophotope C was represented by 35 trial sites, Dc – by 44, Dac – by 76, Dn – by 128, De – by 37, E – by 19 forest ecosystems, accordingly. The relative number of saprophages reaches maximum values in hygro-mesophilic, meso-hygrophilic and hygrophilic conditions, and minimum values – in mesophilic conditions of moistening. The share of rare species is maximum in hygro-mesophilic conditions of moistening. The minimum quantity of mass species is also observed in conditions of hygro-mesophilic and meso-hygrophilic deciduous forests. With the growth of moistening of the soil, quantity of species of Carabidae, Formicidae and other dominant families remains without significant changes. The relative number of Formicidae is maximum in xeromesophilic and mesophilic conditions of soil moistening. In these hygrotopes, as well as in hygro-mesophilic conditions of moistening the Julidae numbers are maximum. The Isopoda percent in mesofauna significantly grows in meso-hygrophilic and hygrophilic conditions of moistening. The share of other dominant taxonomical groups in the structure of litter mesofauna remains without significant changes in numbers. In the majority of the analysed hygrotopes 7–8 families are withing the structure of dominants. In the conditions of salinization (trophotopes De and E), and also on light sandy loam soils, the numbers of litter mesofauna decrease. Share of saprophages is minimum in trophotopes Dc and E, while it increases in trophotopes C, Dac, Dn and De. The dimensional structure of litter mesofauna of trophotopes Dac and Dn comes nearer to optimum. The maximum quantity of Carabidae species is revealed in Dn trophotope. The quantity of Formicidae species increases in trophotopes De and E. The number of Formicidae species is maximum in the forest ecosystems of trophotopes De and E. The share of Isopoda is maximum in the forest ecosystems of trophotope De.

Patterns in the horizontal structure of litter invertebrate communities in windbreak plantations in the steppe zone of the Ukraine

Abstract The article analyses the patterns in the horizontal structure of litter invertebrate communities in windbreak plantations in the Steppe zone of the Ukraine. The number of invertebrate species shows statistically insignificant changes depending on the extent of the litter horizon development. With an increase in litter mass from 300 to 900 g/m2 the number of invertebrate species increases. An increase in the total number of macrofauna is observed in areas having a minimum and maximum thickness of the litter layer. Maximum values in the Shannon diversity index were observed in areas with sparse litter (50–150 g/m2). An observed increase in the variety of macrofauna species were seen where there was sparse grass cover in windbreak planted areas. The total number of litter invertebrate individuals related to the percentage of projective cover of herbaceous plants shows a significant increase in plots with 20–28% cover, though this factor does not affect the number of Aranei, Carabidae, and Staphylinidae. There is a decrease in the number of litter invertebrate species in areas with higher numbers of Lasius platythorax Seifert, 1991, while there is an insignificant change in the overall numbers of macrofauna. The abundance of Myrmica scabrinodis Nylander, 1846 does not show a significant influence on the number of litter macrofauna species. The minimum values of the Shannon biodiversity index for macrofauna were registered in plots with maximum numbers of M. scabrinodis. With an increase in the abundance of ants, the abundance of litter saprophages and phytophages decreases. There are also significant changes in the dominance structure of other taxonomic groups. Biotic factors have greater significance for the horizontal structure of litter macrofauna of steppe plantations than abiotic factors.

Weeds mediate the level of intraguild predation in arthropod food webs

AbstractIntraguild predation, which is common for generalist predators, is a specific form of omnivory that may suppress the biological control of a pest. The dietary flexibility of a given organism depends on the choice of the C3 (banana crop) and the C4 (weeds) pathways they use and on the trophic level on which they feed. Understanding the conditions in which intraguild predation decreases biological control is a major issue in agroecosystems. We tested whether the contribution of different primary producer pathways in diets of generalist predators mediates the level of intraguild predation. We studied 10 agroecosystems in which banana plants (C3 metabolism) were diversely associated with weeds (C4 metabolism). Diversity in litter macrofauna was relatively low, with a mean between three and eight species per trap. Measurement of stable isotopes showed a significant decrease in the δ15N values of generalist predators when the C4 pathway contributed more than the C3 pathway to their diet. We rejected hypotheses that an increase in the abundance of prey and that a decrease in prey's δ15N values occur when the C4 pathway contributes more than the C3 pathway to their diet. The results are consistent with the diet modification hypothesis, that is, intraguild predation is lower when the C4 (weeds) pathway is preferred to the C3 pathway. Our results suggest that when the C4 pathway of weeds is more exploited by herbivores (or detritivores), generalist predators tend to consume these herbivores and thus neglect the intraguild prey. The diverse C4 plant community probably supports a diverse herbivore community that provides alternative prey. Our results provide evidence that increasing plant diversity in agroecosystems should decrease intraguild predation of generalist predators and should therefore improve pest regulation. In an applied perspective, plant diversity could be increased by establishing a more diverse cover‐crop community.

Influence of fallen coarse woody debris on the diversity and community structure of forest-floor spiders (Arachnida: Araneae)

Purely observational studies have documented differences in the abundance and diversity of several litter-dwelling arthropods between sites adjacent to, and far from, CWD, which suggests that reduction of fallen coarse woody debris (CWD) in temperate forests by traditional forestry practices may affect the litter arthropod community. As few field experiments have directly tested the impact of CWD on arthropods inhabiting the litter at different distances from CWD, we removed CWD from replicated open plots on the floor of a second-growth deciduous forest in order to reveal the causal connection between CWD and litter-dwelling spiders, often the most diverse and abundant predators among the litter macrofauna of temperate forests. We also documented the impact of the CWD manipulation on spider prey and several other major macroarthropod groups. Before removing CWD (∅ = 14.3 ± 0.7 cm), we measured response variables as a function of distance (0.5–1.5 m) from CWD in both removal and control plots. In agreement with results of previous research that solely utilized this observational approach in temperate forests, volume and dry mass of litter, spider diversity, overall spider density, and densities of 8 of 16 major spider genera were higher adjacent to CWD before experimental manipulations. Removing CWD reduced the amount of litter and the density of spiders in litter close to where the CWD had been. Removing CWD also altered spider community structure, which had differed between litter sites adjacent to, and far from, CWD prior to the experimental removal of CWD. The patterns, though, were not completely congruent, as some of the taxa affected by the manipulation had not differed between sites prior to the removal of CWD, and vice-versa. Our findings suggest that complex interactions among structural, biotic and microclimatic factors underlie the observed responses to CWD removal by spiders and other arthropods in the litter layer. We also conclude that drawing inferences solely from observational studies is not a reliable approach for predicting the impact of changes in the amount of CWD on arthropods of forest-floor leaf litter. Further field experiments manipulating different volumes of CWD are needed in order to determine the minimum amount of CWD that should be kept on the forest floor of managed forests in order to maintain densities and diversities of major leaf-litter arthropods.

Macrofauna da liteira em sistemas agroflorestais sobre pastagens abandonadas na Amazônia Central

As densidades (ind/m2) e biomassas (mg/m2) de grupos selecionados da macrofauna da liteira (isópodos, diplópodos c cupins) foram estudadas sob diferentes sistemas agroflorestais (SAFs) implantados em áreas de pastagens degradadas c abandonadas na Amazônia central. O estudo foi feito na Estação de Pesquisa Agroflorestal da EMBRAPA/CPAA, 70 km ao norte de Manaus, usando-sc três blocos ao acaso, com cinco tratamentos, em quinze parcelas de 3000 m2; cada bloco tinha quatro diferentes tipos de SAFs e uma capoeira (CAP), usada como controle, onde se manteve a regeneração natural existente. Os SAFs eram dois sistemas agrossilviculturais, um com base em palmeiras e outro mais diversificado, denominado multiestrato, e dois sistemas agrossilvipastoris, de altos e baixos insumos. Em cada parcela, foram coletadas 50 amostras da macrofauna da liteira, usando-se um quadro de madeira de 50 x 50 cm, nas estações chuvosa e seca. A densidade e biomassa da macrofauna foram maiores no SAF mais diversificado (multiestrato) e geralmente maiores sob liteiras de cupuaçu e palmeiras, destacando-se o grupo dos isópodos com as maiores densidades c biomassas, seguido pelos diplópodos, nos SAFs, e pelos cupins, na capoeira. Todos os SAFs apresentaram maiores densidades e biomassas da macrofauna do que a capoeira, indicando a formação de micro-sítios favoráveis à sua ação, devido à melhor qualidade da liteira produzida e/ou da abundância localizada de liteiras de menor qualidade produzida pelas diversas espécies plantadas. Os resultados sugerem a melhoria do funcionamento dos processos de reciclagem no solo e, assim, das perspectivas de sustentabilidade da produção.

Distribution patterns of the litter macrofauna in agroforestry and monoculture plantations in central Amazonia as affected by plant species and management

Within heterogeneous land-use systems such as agroforestry or mixed tree crop plantations, the different morphological and physiological characteristics of the plants, together with their species-specific management, lead to a mosaic of different living conditions for the litter fauna. This may, in turn, influence the processes of decomposition and nutrient cycling and, thus, the growth-conditions of the plants. We studied the effect of different plant species on the litter macrofauna by collecting macro-invertebrates in the litter layer of an agroforestry system composed of four regionally important tree crop species in central Amazonia: cupuaçu ( Theobroma grandiflorum), annatto ( Bixa orellana), Brazil nut ( Bertholletia excelsa) and peach palm ( Bactris gasipaes), with the leguminous cover crop Pueraria phaseoloides and spontaneous grasses as soil cover. The agroforestry system was studied at two fertilisation levels and was compared with a peach palm monoculture. We found invertebrates belonging to 18 orders and 44 families. The number of fauna individuals per unit area differed significantly between plant species within the agroforestry system. Both the number of individuals and the faunal biomass increased linearly with litter dry matter per unit area. The Shannon–Wiener index of family diversity showed a non-linear increase with increasing sampling area and litter mass in the samples, approaching saturation values between 2 and 2.5. The highest faunal abundance and diversity was found in the litter of the peach palm monoculture, apparently due to the stable and protected habitat provided by the fleshy offshoot remains from the palm harvests. The two fertiliser levels only differed with respect to two invertebrate groups, snails and isopods. The results indicate that the creation of a litter and/or mulch layer of at least 3 Mg ha −1, but preferably 6 Mg ha −1 and the association of tree and cover crop species whose litter has a favourable effect on the fauna with species whose litter has a less favourable effect are suitable management tools for the conservation of an abundant and diverse litter fauna in plantations and agroforestry systems of the humid tropics.

Decomposition of litter in sub‐alpine forests of Eucalyptus delegatensis, E. pauciflora and E. dives

AbstractThe rate of decomposition of summer leaf‐fall (abscised leaves), winter leaf‐fall (containing some green leaves) and mature green (picked) leaves was assessed in sub‐alpine forests of E. delegatensis (R. T. Baker), E. pauciflora (Sieb. ex Spreng) and E. dives (Schau.) in the Brindabella Range, Australian Capital Territory, using litter bag and tethered leaf techniques. The relative contribution of leaching, microbial respiration and grazing by invertebrate macrofauna to loss of leaf weight was determined. The effect of leaching and microbial respiration was assessed in terms of weight loss per unit area of leaf (specific leaf weight), while losses due to macro‐faunal grazing were assessed by measuring reductions in leaf area. Litter decomposition constants for litter components (leaf, bark, wood) and total litter were determined from long‐term records of litterfall and accumulated litter.Weight losses of abscised leaves during the initial 12 months ranged from 25% for E. pauciflora to 39% for E. delegatensis and were almost entirely due to reduction in specific leaf weight. Losses in the weight of leaves falling in winter ranged from 38 to 49%, while green leaves lost 45 ‐ 59%. Approximately 50% of the total weight loss of green leaves was due to a loss in leaf area caused by skeletonization by litter macrofauna. Thus abscised leaves rather than green leaves must be used for measuring litter decomposition rates since abscised leaves constitute most of the litterfall in eucalypt forests.Leaves placed in the field in autumn decomposed slowly during the first summer, while the rate increased during the second winter and summer. Low litter moisture content appears to limit decomposition in the initial summer period in all communities, after which litterfall provides a mulch which reduces the rate of desiccation of lower litter layers. A simple linear regression model relating decomposition rate to the number of days (D) when litter moisture content exceeded 60% ODW accounted for 63‐83% of the variation in decomposition of leaves in the field. Inclusion of mean monthly air temperature (T) and the product of D and T (day degrees when litter was wet) in a multiple linear regression increased the variation in decomposition accounted for to 80 – 90%.The rate of weight loss showed a positive linear relationship with the initial concentration of nitrogen (N) or phosphorus (P) in the leaf. These concentrations are an index of the decomposability of leaf substrates (e.g. degree of sclerophylly or lignification).The rate of loss of specific weight was similar for tethered leaves and for leaves enclosed in mesh bags. Measured loss in specific leaf weight after 70 – 90 weeks was less than that predicted using decomposition constants (k).