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1.
《African Zoology》2013,48(2):281-286
The histology of brain neurosecretory cells and the development of the ovary and oocytes of preclitellate, early clitellate and late clitellate stages of Eudrilus eugeniae reared in clay loam soil and pressmud have been studied. E. eugeniae reared in pressmud showed earlier differentiation of lobules in the ovary, and increasedoocyte numbers with larger cellular and nuclear volumes than those reared in clay loam soil. This indicates the nutritional superiority of pressmud over clay loam soil in supporting gametogenesis. In the preclitellate stage, the brain neurosecretory cell types (A and B) are small and appear to be laden with secretory substances. The neurosecretory cells become vacuolated and show increased cellular and nuclear volumes and nucleocytoplasmic indices during the reproductively active clitellate stages. Secretory activity of neurosecretory cells occurs earlier in worms reared in nutritively rich pressmud which has greater amounts of nitrogens, phosphorus and sugar, than in worms reared in clay loam soil.  相似文献   

2.
《African Zoology》2013,48(2):235-244
The abundance of earthworms in the ecological zones in Nigeria has been determined and the possibility of earthworm functions replacing both mechanized land preparation and organic fertilizers discussed. The most abundant earthworms, comprising 62 % of the population, were the advantageous solid-wormcast makers. Mixed Leguminous Wooded Savanna had the highest earthworm density (1.50 million worms/ha), while Wooded Savanna had the lowest (0.23 million worms/ha). Coastal Forest and Mangrove (0.51 t/ha) had the highest earthworm biomass and Afziela Savanna/Semi-Deciduous Forest (0.03 t/ha) had the least. A new soil impact index (SIINDEX) is introduced, which simultaneously incorporates both earthworm biomass and density. The highest SIINDEX was from Mixed Leguminous Wooded Savanna (0.72) and the lowest from Afziella Savanna/Semi-Deciduous Forest (0.11). Forests with SIINDEX less than 0.2 should be regarded as endangered, because their earthworm functions are too low to accomplish significant leaf-litter breakdown and recycling. We suggest that if the illegal annual bush burning is prevented, the soil surface will be naturally mulched, earthworms protected, and by their function in the soil, the need for soil mechanization and fertilization could be replaced by earthworms to produce natural foods.  相似文献   

3.
Surface litter protects rangeland soils against wind and water erosion and provides food and nesting materials for wildlife and insects. However, the ability of grassland systems to provide these services depends on the little studied topic of seasonal surface litter decomposition. Seasonal and annual surface litter decomposition rates were determined between 2014 and 2015 in central and western South Dakota at three mixed-grass prairie locations. Residue bags containing surface litter were placed in the field in late fall (1 November) of 2014 and removed after the winter (1 April), spring (1 July), and summer + fall seasons (1 November) of 2015. The litter was analyzed for total C, total N, acid detergent fiber (ADF), and acid detergent lignin (ADL). Average winter temperatures ranged from −5oC to −15oC, while summer temperatures ranged from 10oC to 35oC. Litter decomposition was lowest during the winter (0.57−0.86 g [kg × day]−1) and greatest during the summer + fall (2.12−2.69 g [kg × day]−1). Over the entire season, 40.8−62% of the surface litter decomposed. Winter litter decomposition was positively correlated with air temperature (r = 0.62, P < 0.01) and snow depth (r = 0.61, P < 0.01), and negatively correlated with C/N ratio (r = −0.65, P < 0.01), ADF (r = −0.35, P < 0.05), and ADL (r = −0.25, P < 0.05) concentrations. These findings indicate that winter decomposition cannot be ignored and that winter surface litter decomposition increases with snow depth.  相似文献   

4.
Plant litter decomposition is one of the most important links connecting plants to the soil through the carbon (C) and nitrogen (N) cycles. Climate change scenarios predict changes in precipitation and N deposition, and previous studies have demonstrated that increases in the availability of water and N affect the litter decomposition rate and nutrient release. We studied the effects of increased N deposition and precipitation on changes in the remaining mass and the C and N contents of shoot litter after decomposition in a typical steppe in Inner Mongolia, China. The treatments included the addition of NH4NO3 at rates equivalent to 0, 25, 50, and 100 kg ? N ? ha? 2yr? 1 with and without added water. The addition of water proved to be a more effective practice than amendment with NH4NO3 for improving the litter decomposition rate; the addition of water significantly increased the rate of litter decomposition (P < 0.001), whereas the addition of N alone had no apparent effect on litter mass loss. However, a repeated measures analysis of variance (ANOVA) showed that the interaction of water and N significantly affected both mass loss and litter N content (P < 0.05), and a linear relationship was identified between litter mass loss and litter decomposition time (P < 0.001). No correlation was found between litter mass loss and organic C content, but a significant positive correlation was found between residual litter mass and N content (P < 0.01). Although the study was conducted over a relatively short period, our results indicate that increased precipitation could potentially promote litter decomposition, whereas increased N input has little effect. The effects of time on litter mass loss and residual C and N concentrations indicate the need for long-term trials that measure the complete process of litter decomposition and the peaks of C and N release.  相似文献   

5.
Terrain can influence vegetation composition, diversity, and biogeochemical cycling in grassland ecosystems. Solar radiation, soil temperature, and moisture distribution are dependent on terrain, which, in turn, can affect plant community structure, rate of litter mass decomposition, and carbon, nitrogen, and phosphorus release. A litter decomposition experiment was conducted over 12 mo at a site representing typical steppe grasslands to better understand the effects of terrain on biogeochemical cycling. The study site had both northeast (shaded) and southwest (sunny) facing aspects with each aspect having three slopes: 15°, 30°, 45°. Litterbags were used for collection of plant community litter from each location. The results indicated that slope and aspect both have significant effects on decomposition rate of litter mass and release rate of C, N, and P. The most rapid decomposition rate of litter mass was on 45° sunny slopes (k value 1.82 × 10‒3 d−1). The most rapid release of C was on 30° shaded slopes with release rate of 4.54 g C yr‒1. The release rate of N decreased with increasing slope steepness but was more rapid on shaded compared with sunny slopes. The most rapid release of P (10.51 mg P yr‒1) occurred on 45° shaded slopes. The total effects of solar radiation and soil temperature on litter mass decomposition were larger, with 0.91 and 0.93, respectively. Soil temperature, litter functional diversity, and initial C/N had positive effects on the litter C release. The release of litter N was mainly promoted by soil temperature. Soil moisture appeared to promote the release of litter P. Overall, terrain influenced litter mass decomposition and C, N, and P release by its effect on the distribution of solar radiation, soil temperature and moisture, and through modification of functional diversity, initial C/N ratios, and water content of litter in typical steppe.  相似文献   

6.
Plant litter and livestock excreta are two important ways of carbon and nutrient input to soil in grassland grazing systems. Grazing livestock often deposit dung on plant litter, which may affect litter decomposition through a changing microenvironment. We assessed effects of yak dung on litter mixing effects on litter decomposition in a Tibetan alpine grassland. Six common species were selected, including low-quality litter species Kobresia capillifolia, Elymus nutans, and Ligularia virgaurea and high-quality litter species Anemone rivularis, Saussurea nigrescens, and Thermopsis lanceolata. Litter bags containing each species alone and all two-species combinations were allowed to decompose with and without experimental dung addition in the field. Mass loss of the leaf litter was measured after 6 and 12 mo. High-quality litter species had significantly greater mass loss than low-quality litter species. Dung significantly accelerated litter mass loss after both 6 and 12 mo for low-quality litter species, but only after 12 mo for high-quality litter species. Litter mixtures containing both high- and low-quality species showed positive nonadditive effects (NAEs) on mass loss after 6 mo but additive effects after 12 mo. Dung increased the strength of NAEs after 6 mo and shifted litter mixing effects from positive to negative NAEs after 12 mo. Our results support previous findings that litter mixing could produce NAEs on litter decomposition and that these NAEs could change with incubation time. Most importantly, we show that dung can modify NAEs, demonstrating that litter mixing effects are dependent on the microenvironment. Our findings also demonstrate that yak dung can influence soil processes by varying both single-species litter decomposition rates and litter interactions within mixtures. Furthermore, the results suggest yak dung is closely related to material and nutrient cycling, so we believe dung should remain and not be substantially removed from this grazing ecosystem.  相似文献   

7.
Responses to stocking density (SD), dietary biotin concentration and litter condition were evaluated on 2016 Ross 308 male broilers in the fattening period (day 22–day 42). The birds were placed in 48 pens with either dry or wet litter to simulate the final stocking density of 30 kg (12 broilers/m2; normal stocking density, NSD) and 40 kg (16 broilers/m2; high stocking density, HSD) of body weight (BW)/m2 floor space. A corn–soybean meal‐based diet was supplemented with biotin to provide a normal (NB; 155 μg/kg) or high (HB, 1521 μg/kg) level of dietary biotin. There were six repetitions per treatment. The inappropriate moisture content of litter associated with HSD was avoided (p < 0.05) by good management (SD difference: dry litter, 6.65% vs. wet litter, 13.23%; 42 days), which made it advantageous (p < 0.01) for footpad (SD difference: dry litter, 0.118 vs. wet litter, 0.312; weekly average value) and hock health (SD difference: dry litter, 0.090 vs. wet litter, 0.303; weekly average value) of HSD birds, but not (p > 0.05) for growth and processing yield. In HSD, the biotin effect (gains, FCR) was significantly higher (p < 0.01) than in NSD. The similar response of HSD birds to supplemental biotin was observed (p < 0.05) for lesion scores of footpad and hock in particularly finishing chickens, and a significant interaction (p < 0.01) among stocking density, biotin supplementation and litter condition existed from 35 to 42 days of age. Taken together, increasing dietary biotin improves the performance and well‐being of broiler chickens stocked at high densities in litter‐independent and litter‐dependent manners respectively.  相似文献   

8.
In order to determine the potential of the earthworm Eudrilus eugeniae as waste processor and protein producer, the life history of this species was studied. The development, growth and reproduction of E. eugeniae were studied. Cattle dung was used as substrate with a moisture content of 70–80% and a temperature of 25°C. Data were gathered over a period of 300 days. It was found that cocoon production started within 24 h after copulation and can be sustained for at least 300 days. Cocoons are produced at an average rate of 1,65 cocoons per worm per day. The mean incubation period of cocoons is 16,6 days with a hatching success of 84% and 2,7 hatchlings per cocoon that hatched. Sexual maturity is attained by the offspring within 40 to 50 days after hatching. E. eugeniae is compared to other vermicomposting species.  相似文献   

9.
李倩  袁玲  杨水平  黄建国 《草业学报》2015,24(9):121-129
黄花蒿主要通过植株残体向土壤释放化感物质,影响土壤肥力和生产力。本试验开展了土壤微生物对黄花蒿凋落物和青蒿素的响应研究。结果表明,在土壤中添加黄花蒿凋落物和青蒿素,真菌数量增加,但显著降低放线菌、自生固氮菌、硝化细菌和亚硝化细菌的数量,不利于土壤有机质矿化,生物固氮和硝化作用。黄花蒿凋落物和青蒿素降低微生物熵,增大代谢熵,说明土壤微生物代谢受到干扰,活性降低。此外,黄花蒿凋落物和青蒿素还使土壤微生物标记性磷脂脂肪酸总量和种类以及细菌、放线菌和原生动物标记性磷脂脂肪酸减少,选择性地抑制了土壤微生物的繁殖生长。在黄花蒿凋落物、青蒿素和对照(不加凋落物和青蒿素)的土壤中,微生物种群结构差异显著,黄花蒿凋落物和青蒿素降低微生物多样性和均匀度指数。因此,在大规模集约化种植黄花蒿的过程中,进入土壤的凋落物抑制有益微生物生长繁殖,改变土壤微生物群落结构,种群减少,密度降低,这可能是黄花蒿抑制后茬和周围植物生长,进而造成减产的重要原因之一。  相似文献   

10.
Rodent pests severely damage agricultural crops. Outbreak risk models of rodent pests often do not include sufficient information regarding geographic variation. Habitat plays an important role in rodent–pest outbreak risk, and more information about the relationship between habitat and crop protection is urgently needed. The goal of the present study was to provide an outbreak risk map for the Dongting Lake region and to understand the relationship between rodent–pest outbreak variation and habitat distribution. The main rodent pests in the Dongting Lake region are Yangtze voles (Microtus fortis). These pests cause massive damage in outbreak years, most notably in 2007. Habitat evaluation and ecological details were obtained by analyzing the correlation between habitat suitability and outbreak risk, as indicated by population density and historical events. For the source‐sink population, 96.18% of Yangtze vole disaster regions were covered by a 10‐km buffer zone of suitable habitat in 2007. Historical outbreak frequency and peak population density were significantly correlated with the proportion of land covered by suitable habitat (r = 0.68, P = 0.04 and r = 0.76, P = 0.03, respectively). The Yangtze vole population tends to migrate approximately 10 km in outbreak years. Here, we propose a practical method for habitat evaluation that can be used to create integrated pest management plans for rodent pests when combined with basic information on the biology, ecology and behavior of the target species.  相似文献   

11.
Improvement in litter traits is the key to profitable pig farming that directly enhances the economic standing of the farmers in developing countries. The present study aimed to explore oestrogen receptor (ESR), epidermal growth factor (EGF), follicle-stimulating hormone beta subunit (FSHβ), prolactin receptor (PRLR) and retinol-binding protein 4 (RBP4) genes as possible candidate genetic markers for litter traits in indigenous pigs of India. The breeds included in the study were Ghungroo, Mali, Niang Megha and Tenyi Vo, and the reproductive traits considered were litter size at birth (LSB), number born alive (NBA), litter weight at birth (LWB), litter size at weaning (LSW) and litter weight at weaning (LWW) at their first parity. PCR-RFLP and primer-based mutation detection methods were used to identify polymorphism, and associations between the genotypes and the traits were analysed using a general linear model. The Ghungroo pigs recorded the best litter performances among the breeds (p < .05, LWB p < .01). Different alleles and genotypes of the genes under study were detected. Short interspersed nuclear element (SINE) −/− genotype of FSHβ revealed significantly higher litter traits (p < .05, LSB p < .01). The LWW was also found to be significantly influenced by ESR BB and AB, EGF AB and BB, and PRLR CC genotypes (p < .05). Although we did not find statistically significant and consistently superior litter traits with respect to different genotypes of other studied genes than genotype SINE −/− of the FSHβ, PRLR CC genotype demonstrated superior performances for all the litter traits. Our study revealed the FSHβ as a potential candidate genetic marker for litter traits in indigenous pig breeds of India.  相似文献   

12.
羊草草原主要凋落物分解及土壤动物的作用   总被引：2，自引：0，他引：2  
对羊草草原主要植物凋落物的分解及分解过程中土壤动物群落作用的研究结果表明,不同凋落物以及在不同网孔网袋中的分解速率存在差异,不同凋落物以虎尾草分解速率最快, 在4和2 mm网袋中分解速率明显快于0.01 mm网袋。凋落物分解过程中土壤动物群落组成以革螨亚目,辐螨亚目和甲螨亚目为优势类群;长蝽科、啮虫科、土蝽科、山跳虫科、驼蝽科、等节跳虫科和管尾亚目为常见类群。 土壤动物促进了凋落物的分解,不同类型土壤动物在凋落物分解中的贡献不同,中小型土壤动物起到最为显著的促进作用。凋落物重量损失率同土壤动物群落特征的相关分析结果显示,羊草草原凋落物的重量损失率与土壤动物群落的多样性指数、丰富度指数间存在显著的负相关关系,而凋落物重量损失与土壤动物群落其他特征无明显相关关系。  相似文献   

13.
The objective of this study was to investigate the effects of dietary supplementation with various fat sources (3.8–3.9% of diet) during late pregnancy and lactation on the reproductive performance, fatty acids profile in colostrum, milk and serum of sow progeny. A total of 80 multiparous sows were randomly fed a control (adding no oil), palm oil (PO), fish oil (FO) or soybean oil (SO) supplemented diet from 90 days of pregnancy to weaning. Supplementation of FO increased litter size of weak piglets, compared with the control‐fed sows (P < 0.05). Dietary FO and SO supplementation, enhanced the weaning survival rate, litter weaning weight, litter weight gain and fat content in milk (P < 0.05). The highest immunoglobulin (Ig)G and IgM levels in colostrum and milk were observed in the FO group (P < 0.05). Meanwhile, the highest concentration of C22:5 (n‐3) and C22:6 (n‐3) in colostrum, milk and piglet serum was observed in the FO group (P < 0.05). Taken together, dietary inclusion of FO or SO improved growth performance of nursing piglets by increasing milk fat output, and FO consumption by sows might benefit the piglets via increasing n‐3 polyunsaturated fatty acid availability and immunoglobulins (IgG and IgM) secretion.  相似文献   

14.
云南马龙县山地封育草地凋落物分解与氮释放的研究   总被引：4，自引：3，他引：1  
以云南马龙县退化山地草地为研究对象,对封育2年草地的凋落物、土壤水分、凋落物含水率,以及氮素释放进行了研究.结果表明.围栏封育草地凋落物分解速率显著高于未封育草地凋落物分解速率(P<0.05),封育区凋落物增加.起到了一定的保温作用,即可以加速凋落物的分解.同时也减少冬季低温对山地草地的伤害;草地凋落物的干物质分解速率与土壤含水率、凋落物含水率呈显著正相关(r=0.949,P<0.05),封育增加了土壤的含水率,促进了凋落物的分解.总氮的含量与凋落物分解速率成正相关(r=0.995,P<0.05).氨素是调节草地凋落物分解速率的一个重要因素.  相似文献   

15.
Long-term overgrazing has significantly changed plant species composition in rangeland ecosystems, and this change may alter ecosystem functioning remarkably. In this study, decomposition rates and nutrient dynamics of pure litter (leaf, stem, or root litter) and 11 litter mixtures (from two to five litter components), including nine aboveground litter mixtures and two root litter mixtures, of five common plant species in degraded semiarid rangelands of northern China were studied for 1 yr. We found that fine root litters generally decomposed faster and had faster nutrient turnover rates than leaf and stem litters. The decomposition rates of leaves and stems were significantly and positively correlated with initial litter nitrogen (P < 0.01) and phosphorus contents (P < 0.05), and the decomposition rates of fine roots were significantly and negatively correlated with initial litter carbon:nitrogen ratios (P < 0.05). Nonadditive effects were found in six out of the nine aboveground litter mixtures (three positive and three negative). There were only additive effects on decay rates and nutrient fluxes in the two root litter mixtures. The occurrence and direction of nonadditive effects were dependent on the properties of component litters and had no obvious correlations with litter diversity. Negative mixing effects on nutrient immobilization can facilitate the release of some important nutrients during litter decomposition processes, and further help to accelerate nutrient cycling in such semiarid rangeland ecosystems. Our results indicate that change of plant species composition by overgrazing may slow down the mass loss rates, but may not necessarily impact the release of some nutrients.  相似文献   

16.
Data on litter production and decomposition in an arid rangeland in Kenya was collected over a two-year period. Utter sampling was carried out at monthly intervals using a rectangular 0.25m?2 quadrat frame. Utter within the quadrats was handpicked and washed with running water to get rid of soli particles, dried, and weighed. Weights were expressed on organic matter basis. Monthly litter production ranged from 31.4g m?2 to 130.0g m?2. Mean monthly yield was 92.5 ± 26g m?2, with a 28% coefficient of variation. There was no significant difference (p>0.01) in litter yield between 1992 and 1993. Rate of decomposition for aboveground material ranged from 0.005g g?1 day?1 to 0.084g g?1 day?1. The mean annual rate of decomposition was 0.026g g?1 day?1. Belowground plant material rates of decomposition spread from 0.009g g?1 day?1 to 0.062g g?1 day?1. with a mean annual rate of 0.041g g?1 day&minus1. Belowground material consistently decomposed faster than aboveground material. Peaks in both aboveground and belowground material decomposition rates coincided with rainfall peaks. Overall, in this arid environment, litter production and decomposition is pursed in nature, and trends are closely related to rainfall occurrence. Moisture is thus a limiting factor both to the production and decomposition of litter. Belowground litter plays a significant role in nutrient cycling.  相似文献   

17.
温带果园护土生草鼠茅草的腐解和养分释放   总被引：3，自引：0，他引：3  
鼠茅草是适合于温带果园的越年生护土生草,有助于防止水土流失,然而果农担心鼠茅草可能与果树争肥,不利于果树生产。本研究在青岛地区温湿气候条件下测试鼠茅草的腐烂分解及养分释放特征。2012年6月底采集枯死鼠茅草,将其埋在10 cm深的土壤中,使土壤含水量分别稳定在田间持水量的65%,75%和85%,7－10月份每隔10 d抽检其腐解程度和碳、氮、磷、钾元素的释放速率。结果表明,鼠茅草的腐烂分解是比较快的,自初夏枯死后经80 d大约分解30%;伴随鼠茅草的腐烂,碳、氮、磷和钾会释放出来,快速释放期集中在前20－40 d,钾的释放速度最快,其次为磷,碳、氮的释放速度较慢;土壤含水量影响鼠茅草的腐解过程,当土壤含水量由65%田间持水量提高至85%时,鼠茅草的腐解和养分释放加快。据此可断,7-10月是鼠茅草分解的主要时期,可为果树生长提供营养而非争夺养分。在青岛等温湿地区,以鼠茅草作为果园护土生草是可行的,它们同苹果等落叶果树在养分利用上可形成互补关系,有益于果园的养分循环和持续生产。  相似文献   

18.
The aim of this paper was to present the main results obtained in Cuba on the effects of feeding tropical trees and shrubs on rumen methanogenesis in animals fed with low quality fibrous diets. More than 20 tree and shrub foliages were screened for phytochemicals and analyzed for chemical constituents. From these samples, seven promising plants (Samanea saman, Albizia lebbeck, Tithonia diversifolia, Leucaena leucocephala, Trichantera gigantea, Sapindus saponaria, and Morus alba) were evaluated for methane reduction using an in vitro rumen fermentation system. Results indicated that the inclusion levels of 25% of Sapindo, Morus, or Trichantera foliages in the foliages/grass mixtures (grass being Pennisetum purpureum) reduced (P < 0.01) methane production in vitro when compared to Pennisetum alone (17.0, 19.1, and 18.0 versus 26.2 mL CH4/g fermented dry matter, respectively). It was demonstrated that S. saman, A. lebbeck, or T. diversifolia accession 23 foliages when mixed at the rate of 30% in Cynodon nlemfuensis grass produced lower methane compared to the grass alone. Inclusion levels of 15% and 25% of a ruminal activator supplement containing 29% of L. leucocehala foliage meal reduced methane by 37% and 42% when compared to the treatment without supplementation. In vivo experiment with sheep showed that inclusion of 27% of L. leucocephala in the diet increased the DM intake but did not show significant difference in methane production compared to control diet without this foliage. The results of these experiments suggest that the feeding of tropical tree and shrub foliages could be an attractive strategy for reduction of ruminal methanogenesis from animals fed with low-quality forage diets and for improving their productivity.  相似文献   

19.
细根分解过程中的营养元素释放是低覆盖度植被区土壤物质循环的关键环节,菌根在该过程中的作用目前尚不明确。本研究以退化沙质草地植被恢复过程中的先锋灌木差不嘎蒿为对象,采用内生芯法,分别研究了活细根+菌根、菌根以及无根（对照）处理下其细根分解过程中的营养元素（氮、磷、钾）释放动态。结果表明：菌根对差不嘎蒿细根分解过程中营养元素含量的影响主要发生在分解后期（1 a以后）。当分解超过1 a,菌根的存在显著降低了细根氮含量,这种效应不受活的细根的影响,菌根+活细根以及菌根处理下的氮含量分别较对照低15.3%和9.5%;而对于磷和钾,菌根处理下的含量均显著低于对照（P<0.05）,但该效应受活根的影响,活细根+菌根处理下的差不嘎蒿磷含量与钾含量均与对照无显著差异（P>0.05）;从营养元素的物质残留动态分析发现,菌根显著促进了分解细根中氮素的释放（P<0.05）,这种促进效应主要发生在分解的中期;而对于磷和钾主要发生在分解的后期,且受活细根干扰。研究结果表明,菌根是影响根系分解过程中营养元素释放的关键要素,在植物根系分解及其与土壤物质周转关系的研究中应当重点关注。  相似文献   

20.
羊草草原生态系统的分解者与枯枝落叶分解的研究   总被引：15，自引：2，他引：15  
羊草草原的分解者包括土壤微生物和土壤动物。土壤微生物中的细菌、放线菌和真菌的数量峰值交替出现在７～９月份，该时期正是枯枝落叶分解的旺盛季节。土壤微生物生物量最大值出现在８月份，与枯枝落叶最大损失量相吻合。土壤动物的数量和生物量的季节变化趋势，基本上与枯枝落叶失重变化一致。分解者的不同类群，对枯枝落叶的分解作用不同，分解主要由土壤微生物来完成，分解强度占年损率的９７％，其中放线菌分解能力最强，真菌次之，土壤动物仅占３％。  相似文献   

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