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1.
David H. Wise   《Pedobiologia》2004,48(2):181-188
In a long-term field experiment, densities of wandering spiders (i.e. species that do not build webs to capture prey) were reduced in order to determine whether or not a major group of microbi-detritivores, the Collembola (springtails), would increase in response to lowered spider predation. Thirty 4-m2 fenced plots (15 spider-removal, 15 control plots) and 15 unfenced, undisturbed reference areas were established in a deciduous forest. Spiders were taken from the removal-treatment after being collected by periodic trapping with pitfall traps that contained no preservative, and by searching the litter surface. Judging from a comparison of the numbers captured during periodic censuses in spider-removal and control plots (one census period was two consecutive days of pitfall trapping), wandering spiders were rapidly reduced by ca. 50% and were maintained at levels lower than control plots for 1.3 years. The reduction in numbers was greatest for wolf spiders (Lycosidae; ≈90%). Of six families of Collembola abundant in the leaf litter during the experiment, one family, the Tomoceridae, exhibited a significant release from spider predation. Densities of tomocerids, which are the largest and most active springtails on the research site, gradually increased until they were consistently 2× higher in the spider-removal treatment than in either fenced control plots or unfenced, open reference areas.  相似文献   

2.
Spiders are major predators in forest-floor leaf litter, yet little is known about their impact on prey populations and on forest-floor processes such as litter decomposition. This experiment investigated the effect of removing spiders on Collembola densities. We also examined the potential indirect effect of spider removal on rate of litter disappearance. Twenty-eight 1-m2 plots were randomly assigned to one of four treatments: O – open, no manipulations; F – fenced, no litter sifted, no spiders removed; FS – fenced, litter sifted, no spiders removed; and FSR – fenced, litter sifted, spiders removed. In early August, we sifted the litter in the FS and FSR plots, removing all encountered spiders from the FSR treatment. A month later, we placed into each plot one 15 × 15-cm litterbag filled with a known amount (ca. 3 g) of dried straw. After six weeks, litterbags were collected and fauna were extracted in a Kempson-McFadyen apparatus. Decreasing spider predation increased densities of Collembola, and increased the rate at which straw disappeared from litterbags. These results indicate that spider predation may reduce Collembola densities enough to lower rates of litter disappearance on the forest floor.  相似文献   

3.
Summary The influence of leaf litter from three Salix spp. on fungal growth and microbial decomposition was studied using 1-mm-mesh litter-bags, and the effect on additional soil macrofaunal activity was studied by measuring litter disappearance from 4-mm-mesh bags and under 4-mm-mesh nets. Mineral macro-elements, water-and ethanol-extractable substances, lignin, and protein-precipitating substances (astringency) in the litter were determined, taking contaminating of the litter with soil particles into account. As expected, the litter disappeared more quickly from the large-mesh bags than from the small-mesh bags, which was attributed to earthworm activity. During the 1st year, the rate of leaf disappearance from both types of bags and under the nets was much higher for S. daphnoides than for S. viminalis and S. fragilis. The lower initial astringency, related to the tannin content, of the S. daphnoides litter might account for this difference. Tannin metabolites probably hampered both microbial decomposition and earthworm acceptability for some time also after the astringency was lost. Neither the content of macronutrients nor that of the other organic fractions studied can be assumed to have had any effect on weight losses due to microbial decomposition. Although, the S. daphnoides leaves initially contained the least amount of fungal mycelium (m g-1 dry weight), the increase after contact with soil was most pronounced in this litter. The species composition of Fungi Imperfecti in the leaves of S. viminalis and S. daphnoides differed only for fresh litter, whereas the number of isolates was somewhat higher for S. daphnoides throughout the study. Similar seasonal variations in fungal composition occurred in both the S. viminalis and the S. daphnoides litter.  相似文献   

4.
[目的]开展凋落叶分解速率研究,探讨凋落叶分解速率与初始质量的关系,为甘肃省兴隆山森林生态系统物质循环研究提供依据。[方法]采用凋落物分解袋法,以兴隆山青杄、山杨和白桦3种主要树种的凋落叶为研究对象,进行凋落叶分解速率及凋落叶初始质量的研究,明确凋落叶分解速率与初始质量的关系。[结果]青杄中龄林针叶分解速率为0.16,95%分解期为19.08a;青杄近熟林针叶分解速率为0.13,95%分解期为23.70a;山杨和白桦凋落叶分解速率均为0.11,95%分解期分别为28.57a和27.27a;山杨和白桦凋落叶分解速率明显要小于青杄针叶,这很可能是凋落叶分解主场效应和分解袋孔径较小所致。凋落叶分解速率与氮含量呈显著线性正相关,与木质素含量、碳/氮值、木质素/氮值和钾含量呈显著线性负相关,特别是与木质素含量、氮含量和木质素/氮值,相关系数均达0.700 0以上;钾含量、木质素含量、木质素/氮、碳/磷和纤维素含量是影响兴隆山森林凋落叶分解速率的重要指标。[结论]木质素/氮值是影响凋落叶分解速率的关键质量指标,凋落叶初始木质素/氮值越高,分解速率越低。  相似文献   

5.
The decomposition and nutrient content of litter was studied for 2 years in regrowth Eucalyptus diversicolor forest to which N (0, 200 kg ha-1 year-1) and P (0, 30, 200 kg ha-1) had been applied. The P addition increased, and the N addition decreased, the rate of dry weight loss of decomposing litter. Analysis of the coefficients of a double exponential decay model with components describing the release of labile and resistant fractions indicated that decomposition of the resistant component of litter was most affected by the fertilizer additions. Treatment with N reduced the rate of loss of this component and increased its half-life by approximately 30%, whereas P treatment increased its rate of decay and decreased its half-life by approximately 30%. P accumulated in litter during decomposition. P uptake and retention was greater in P-treated than untreated plots. The application of N reduced P accumulation in litter. An accumulation of N also occurred during decomposition, the amount of N imported into litter being greater on plots treated with N fertilizer. Treatment with N affected the amount of S in decomposing litter. Litter on N-treated plots either accumulated more S or released it more slowly than litter on plots not treated with N. The application of N as NH4NO3 decreased forest-floor litter pH, increased litter layer mass (by 15%), and increased the amount of N (by 34%) and S (by 32%) stored in the forest floor. Treatment with P reduced the amount of N (by 22%) stored in the litter layer. The application of 200 kg P ha-1 in the absence of N increased the store of P in the litter layer by 80%, but when N and P were applied together the amount of P in the litter was not significantly different between P treatments.  相似文献   

6.
《Applied soil ecology》2007,35(3):523-534
Climate-change models predict a more intense hydrological cycle, with both increased and decreased amounts of rainfall in areas covered with temperate deciduous forests. These changes could alter rates of litter decomposition, with consequences for rates of nutrient cycling in the forest ecosystem. To examine impacts of predicted changes in precipitation on the rate of decay of canopy leaves, we placed litterbags in replicated, fenced 14 m2 low-rainfall and high-rainfall plots located under individual rainout shelters. Unfenced, open plots served as an ambient treatment. Litter in the high-rainfall and ambient plots decayed 50% and 78% faster, respectively, than litter in the low-rainfall plots. Litter in the ambient plots disappeared 20% faster than in the high-rainfall treatment, perhaps via greater leaching during heavy rainfall events. Ambient rainfall during the experiment was similar in total amount to the high-rainfall treatment, but was more variable in intensity and timing. We used litterbags of different mesh sizes to examine whether changes in rainfall might alter the impacts of major categories of the fauna on litter decay. However, we found no consistent evidence that excluding arthropods of different sizes affected litter decay rate within any of the three rainfall treatments. This research reveals that changes in rainfall predicted to occur with global climate change will likely strongly alter rates of litter decay in deciduous forests.  相似文献   

7.
Abstract

Litter fall and its decomposition rate play an important role in nutrient recycling, carbon budgeting and in sustaining soil productivity. Litter production and the decomposition rate were studied on commonly planted broad-leaved Eucalyptus (Eucalyptus globulus, Eucalyptus camaldulensis, Eucalyptus saligna) and coniferous (Juniperus procera, Cupressus lusitanica, Pinus patula) plantation species and compared with the adjacent broad-leaved natural forest. The production of litter was recorded by litter traps and the decomposition rate was studied by nylon net bag technique. Litter production under broad-leaved plantation species and natural forest (that varied from 9.7 to 12.6 Mg ha?1 y?1) was significantly higher (p<0.05) than that under coniferous species (that varied from 4.9 to 6.6 Mg ha?1 y?1). The average concentration of C and N in fresh mature leaves was higher than in leaf-litter fall, implying that both C and N were either sorbed in the plant system or lost through decomposition, leaching or erosion during the leaf-litter fall period. The amount of N, which potentially returned to the soil through the leaf-litter fall, tended to be higher in natural forest than in Eucalyptus plantations. The residual litter mass in the litter bag declined with time for all species. The annual dry matter decay constant (k) varied from 0.07 m?1 in Pinus patula to 0.12 m?1 in Eucalyptus saligna. The half-time (t0.5) decay varied from 6.0 for Eucalyptus saligna to 9.7 months for Pinus patula. The results suggest that the decomposition rate in Pinus patula was relatively lower than the other species and the litter production under broad-leaved Eucalyptus was comparatively higher than that in coniferous species. Overall the litter decomposition was fast for all species. The higher litter production and its relative faster rate of decomposition is a positive aspect to be considered during species selection for the restoration of degraded habitats given other judicious management practices such as prolonging the rotation period are adhered to.  相似文献   

8.
Abstract

Plant litter and fine roots are important in maintaining soil organic carbon (C) levels as well as for nutrient cycling. The decomposition of surface‐placed litter and fine roots of wheat (Triticum aestivum), lucerne (Medicago sativa), buffel grass (Cenchrus ciliaris), and mulga (Acacia aneura), placed at 10‐cm and 30‐cm depths, was studied in the field in a Rhodic Paleustalf. After 2 years, ≤10% of wheat and lucerne roots and ≥60% of mulga roots and twigs remained undecomposed. The rate of decomposition varied from 4.2 year?1 for wheat roots to 0.22 year?1 for mulga twigs, which was significantly correlated with the lignin concentration of both tops and roots. Aryl+O‐aryl C concentration, as measured by 13C nuclear magnetic resonance spectroscopy, was also significantly correlated with the decomposition parameters, although with a lower R 2 value than the lignin concentration. Thus, lignin concentration provides a good predictor of litter and fine root decomposition in the field.  相似文献   

9.
In Sudan, tree plantations remain the first choice and are widely used in protecting arable lands from sand movement. Decomposition and nutrient changes from leaves of some agroforestry trees (Eucalyptus microtheca, Ficus spp., and Leucaena leucocephala) and litter fall from guava (Psidium guajava) and mango (Magnifera indica) were monitored (in a 12‐week litter‐bag experiment). Rate of dry‐matter weight loss from guava (0.098 wk?1) was significantly (P < 0.01) faster than from mango residues (0.04 wk?1). Corresponding values for Leucaena, Eucalyptus, and Ficus were 0.0533, 0.0524, and 0.0438 wk?1, respectively. In general, micronutrients tend to accummulate during a decomposition period. Potassium (K) was the only element found to be consistently lost by leaching very rapidly from all litters. Nitrogen (N) was released at a significantly (P < 0.03) higher rate from Leucaena (0.0558 wk?1) compared to Ficus (0.0399 wk?1) and Eucalyptus (0.0301 wk?1). Mobility of nutrients from the litters was in the order of K > phosphorus (P) = N > calcium (Ca) > magnesium (Mg). It is concluded that ficus and mango leaves are suitable for improving quality of arid soils through buildup of soil organic matter and supplying easily released organic sulfur (S) (environmentally sound management practice) whereas litter from guava is suitable for temporary nutrient correction. Mixing of guava and mango residues may slow fast decomposition of the former.  相似文献   

10.
The amount of organic matter and rate of litter decomposition in relation to vegetation type under mediterranean-type forests in southern Tuscany was studied. Since existing concepts are largely based on studies of soils on calcareous substrates in this region, particular attention was paid to soils on non-calcareous materials. The humus type and distribution at five sites on acid metamorphic rocks and at one site on dolomitic limestone with different vegetation types was investigated. The input of above-ground litter was also determined. On the metamorphic rocks, clear trends in humus profile development could be observed from deciduous through sclerophyllous to coniferous vegetation: there was a decrease in litter nitrogen content (9.3 to 5.8 g N kg?1 DM), an increase in the amount of organic matter in ectorganic layers (2.53 to 4.66 kg m?2), a decrease in the decay constant k (0.26 ± 0.02 to 0.17 ± 0.03 a?1), and a decrease in soil faunal activity. The results indicate that, under eu-mediterranean to sub-mediterranean forests, decomposition rates are comparable to those under temperate deciduous forests, and that the dominant humus form is a leptomoder. The spatial variation in the amount of organic matter within the plots was considerable, and was related to vegetation type.  相似文献   

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