连续年龄序列桉树人工林凋落物分解的研究

通过野外定位监测和取样分析,研究了连续年龄序列(3 a,4 a,5 a,6 a)桉树人工林的叶凋落物分解及养分释放动态。结果表明,经过390 d分解后,不同龄级桉树人工林凋落物的残留率分别为31.11%,28.37%,36.70%和46.99%,年平均分解系数分别为0.962 0,0.956 8,0.793 0和0.628 6,周转期分别为3.03,3.07,3.54,4.66 a,说明随着林木龄级的增加凋落物的分解速度逐渐下降。在凋落物分解过程中,N、P、K、Ca、Mg、Mn、Zn和Fe元素,均体现出比较明显的淋溶-富集-释放模式。各年龄段桉树林凋落物N元素的周转期分别为1.65,1.95,2.39,2.96 a,P为1.82,1.48,2.35,3.05 a,K为0.95,1.31,3.27,2.80a,Ca为3.39,2.74,3.49,3.29 a,Mg为1.27,2.03,3.66,2.33 a,Mn为1.98,1.01,2.67,3.38 a,Zn为2.74,1.83,2.92,4.03 a,Fe为2.96,1.07,2.84,3.19 a。从各元素的周转时间可以看出,N、P、K元素的周转速度较快,说明这些元素易淋溶,能更快地归还林地以供应林木生长的需要。     

木荷林凋落物的归还动态及分解特性

通过对杭州常绿阔叶林中凋落物的定位观测研究表明,该系统中年均凋落物量为5.85t/hm2,其中以叶最多,占总量的79.5%,枝果较少,分别占7.1%和13.4%。归还动态呈双峰型,即4月和9月为2次高峰。凋落物的半分解时间为1.59a,分解动态呈指数衰减规律。凋落物的年养分归还量达223.69kg/hm2。木荷林中凋落物的现存量为7.47t/hm2。平均分解率为45.18%。林分中凋落物量还处于增长阶段。     

中国亚热带两种竹林凋落物输入量、凋落物分解和养分释放动态

Bamboos are one of the fast-growing and multiple use species in the world, and thus bamboo forests/plantations play an important role in C sequestration at regional and global levels. We studied aboveground litterfall, litter decomposition and nutrient dynamics for two years in two subtropical bamboo ecosystems in Southwest China so as to test the hypothesis that litter quality determine the rate and nutrient dynamics during decomposition of different litter fractions. Mean annual total aboveground litter production ranged from 494 to 434 g m-2 in two bamboo stands （P stand, dominated by Pleioblastus amarus and H stand, hybrid bamboo dominated by Bambusa pervariabilis x Dendrocalamopsis daii）. Bulk （-80%） of litter production was contributed by leaf litter in two stands followed by twigs and sheathes. Different litter fractions represented considerable variations in the rates of mass loss and nutrient release. Variation of the mass remaining after 2 years of decomposition was significantly explained by initial C/N ratio and initial P concentration. Initial concentrations of N, P, Ca, and Mg explained 57.9%, 95.0%, 99.8% and 98.1%, respectively, of the variations of these elements mass remaining after 2 years of decomposition. The patterns of nutrient dynamics and the final amount remaining were mainly determined by their initial litter substrate quality in tl~ese two subtropical bamboo plantations.     

沙漠化过程对植物凋落物分解的影响

应用分解袋法测定分析了沙漠化过程对凋落物分解及碳氮释放的影响。结果表明,潜在、轻度、中度、重度和严重沙漠化沙地土壤中的凋落物经过110d的分解后,干物质残留率分别为38.5%,40.8%,45.2%,55.6%和58.8%,C残留率分别为37.1%,36.6%,41.4%,53.6%和51.1%,N残留率分别为43.8%,47.6%,54.2%,59.4%和58.9%。说明随着沙漠化程度的增加,凋落物的干物质失重率降低,分解速率减小,C、N释放速率减缓。分解过程中,凋落物在各生境土壤中C的释放速率明显快于N;C含量变化趋势为先下降后略有上升,但总体低于初始C含量;N含量总体表现为上升的趋势。     

植物凋落物分解对土壤有机碳稳定性影响的研究进展

凋落物是植物向土壤输入有机碳的主要途径,源于凋落物的碳一部分以CO₂的形式散失到大气,另一部分以有机碳的形式输入到土壤中,在土壤微生物的作用下经过一系列的周转参与稳定有机质的形成。但土壤作为“黑箱”,凋落物向土壤有机碳转移的过程和作用机理仍不明确。结合国内外该研究领域的主要成果,简要介绍了植物凋落物分解的研究方法、土壤有机碳组分及土壤有机碳稳定性,并从植物凋落物分解对土壤有机碳及其组分、土壤呼吸和激发效应、土壤微生物群落结构及酶活性的影响以及植物-土壤-微生物相互作用过程对有机碳稳定性的影响等方面进行概述,厘清植物凋落物分解与土壤稳定有机碳形成的关系,并提出了未来该领域亟待关注的研究方向和研究内容。     

黄河三角洲不同人工刺槐混交林凋落物分解特性

为研究黄河三角洲不同人工刺槐混交林凋落物分解特性,选取白蜡刺槐混交林、臭椿刺槐混交林、国槐刺槐混交林、榆树刺槐混交林4种混交林,采用凋落物袋法进行为期1年8月的凋落物分解特性研究。结果表明:4种混交林凋落物分解速率变化规律相似,前期分解较快,后期分解较慢。4种混交林凋落物分解系数介于0.55~0.74,其中臭椿刺槐混交林凋落物分解系数最高,榆树刺槐混交林最低;臭椿刺槐混交林凋落物分解周期最短为4.03a,榆树刺槐混交林最长为5.47a。4种混交林凋落物中N、P、K、木质素含量以及木质素/N差异显著(P0.05),凋落物分解速率与其N、P含量呈显著正相关关系,与K含量以及C/N呈显著负相关关系。混交林土壤pH、含水量与凋落物分解系数呈显著正相关关系;电导率、碱解氮、有效磷、速效钾含量与凋落物分解系数呈显著负相关关系,表明土壤pH、含水量升高有利于凋落物分解,而电导率、碱解氮、有效磷、速效钾含量升高则减缓凋落物分解。     

内蒙古皇甫川流域凋落物分解过程中营养元素的变化特征

在内蒙古皇甫川流域,利用凋落物样袋分解法对不同植被类型凋落物分解过程中营养元素的变化特征进行了研究。结果表明:在杨树叶、油松针叶和禾草3种植被凋落物分解过程中,营养元素随凋落物失重率的增高而降低,其中一部分营养元素回归土壤后,使凋落物样袋下相对应土层的营养元素含量提高;凋落物分解对恢复、补充和提高土壤肥力,防止水土流失,具有重要的实际意义。     

杨梅生态园林下凋落物的分解状况分析

在水土流失严重区域发展杨梅林生态园,可以比一般治理区更能改善林下土壤有机质含量,提高土壤肥力,各种生化强度均比一般治理区强,氨化作用、硝化作用、固氮作用和纤维素分解作用分别比一般治理区提高15.2%、60.1%、91.6%、53.8%;土壤中的根际微生物数量高于一般治理区,从而加快了林内凋落物的分解,也有利于植物本身的生长和养分的吸收。     

松、栎纯林及混交林凋落物分解特性研究

松树(Pinus massoniana Lamb.)和栎树(Quescus variabilis BL.)都是我国广为栽培的树种.长期以来,由于松树林地树种单一,群落结构简单和重复连栽的管理方式,林地环境质量已逐渐退化,存在着明显的地力衰退现象[1,2].     

杉木与阔叶树叶凋落物混合分解对土壤性质的影响

通过盆钵模拟试验对杉木与楠木、杉木与木荷叶凋落物混合分解后土壤性质进行研究,结果表明:土壤微生物区系中,细菌占微生物总数的98.18%~99.80%,真菌、放线菌在微生物总量中的比例差异不显著(P>0.05),分别为0.12%~1.01%和0.12%~1.08%;7月份土壤微生物中放线菌数量显著高于3月份土壤微生物中放线菌数量(P<0.05),而细菌数量相对较少;杉木、楠木以及木荷叶凋落物三者单独分解时,阔叶树林地细菌数量较大,杉木林地的真菌、放线菌数量较多。当杉木与楠木叶凋落物混合分解时,土壤三大微生物数量以及微生物总量都明显增加;与木荷叶凋落物混合分解时,仅细菌和微生物总量有所增加。混合分解后,林内土壤养分大体呈低~高~低的变化模式;pH值均有不同程度的,其中增加最多的是杉楠X1+3X2的处理。     

Home-field advantage of litter decomposition and nitrogen release in forest ecosystems

Litter decomposition is a major fundamental ecological process that regulates nutrient cycling, thereby affecting net ecosystem carbon (C) storage as well as primary productivity in forest ecosystems. Litter decomposes in its home environment faster than in any other environment. However, evidence for this phenomenon, which is called the home-field advantage (HFA), has not been universal. We provide the first HFA quantification of litter decomposition and nutrient release through meta-analysis of published data in global forest ecosystems. Litter mass loss was 4.2 % faster on average, whereas nitrogen (N) release was 1.7 % lower at the home environment than in another environment. However, no HFA of phosphorus (P) release was observed. Broadleaf litter (4.4 %) had a higher litter mass loss HFA than coniferous litter (1.0 %). The positive HFA of N release was found in the coniferous litter. Mass loss HFA was significantly and negatively correlated with the initial lignin:N litter ratio. The litter decomposition and N release HFAs were obtained when mesh size ranged from 0.15 mm to 2.0 mm. The HFA of litter decomposition increased with decomposition duration during the early decomposition stage. The HFA of N release was well correlated with mass loss, and the greatest HFA was at mass loss less than 20 %. Our results suggest that the litter decomposition and N release HFAs are widespread in forest ecosystems. Furthermore, soil mesofauna is significantly involved in the HFA of litter decomposition.     

城市林木枯落物与河道底泥不同配比的堆肥效果

为利用城市林木枯落物与河道底泥堆肥生产有机肥,设计城市林木枯落物和经加粉煤灰钝化处理的河道底泥5种不同比例(1∶1、1∶2、1∶3、2∶1和3∶1)的高温堆肥试验,测定堆肥过程中堆温、p H值、有机质和C/N的动态变化,以及这5种配方堆肥产物的种子发芽指数。结果显示,堆温和p H值均呈先升高后下降的趋势,3∶1的配比升温迅速、高温期维持时间(5 d)最长;堆肥结束时,各处理均达到腐熟,p H值在7.47~8.87,有机质分别下降了36%、38%、42%、33%和29%,城市林木枯落物比例增加有利于减少有机质损失;由于底泥的C/N较低,增加枯落物有助于提高堆肥效率;处理1、4和5的种子发芽率分别在26、18和19 d达80%以上,而处理2和3直至堆肥结束其种子发芽率仍小于80%。综合考虑堆肥质量和效率,底泥和城市林木枯落物3∶1的处理为规模化生产有机肥的适宜原料比例。     

Successional changes in microbial biomass,respiration and nutrient status during litter decomposition in an aspen and pine forest

Microbial biomass, microbial respiration, metabolic quotient (qCO₂), C_mic/C_org ratio and nutrient status of the microflora was investigated in different layers of an aspen (Populus tremuloides Michx.) and pine forest (Pinus contorta Loud.) in southwest Alberta, Canada. Changes in these parameters with soil depth were assumed to reflect successional changes in aging litter materials. The microbial nutrient status was investigated by analysing the respiratory response of glucose and nutrient (N and P) supplemented microorganisms. A strong decline in qCO₂ with soil depth indicated a more efficient C use by microorganisms in later stages of decay in both forests. C_mic/C_org ratio also declined in the aspen forest with soil depth but in the pine forest it was at a maximum in the mineral soil layer. Microbial nutrient status in aspen leaf litter and pine needle litter indicated N limitation or high N demand, but changes in microbial nutrient status with soil depth differed strongly between both forests. In the aspen forest N deficiency appeared to decline in later stages of decay whereas P deficiency increased. In contrast, in the pine forest microbial growth was restricted mainly by N availability in each of the layers. Analysis of the respiratory response of CNP-supplemented microorganisms indicated that growth ability of microorganisms is related to the fungal-bacterial ratio.     

Early-stage decomposition of maize litter at different positions in a semi-arid cropland

ABSTRACT

Litter decomposition plays a crucial role in controlling carbon (C) cycling and nutrient turnover in agroecosystems. In this study, the litterbag method was used to investigate the mass loss and nitrogen (N) dynamics of maize litters (culms, leaves and sheaths) at aerial, surficial and belowground positions in the initial 191 d of decomposition. For any tissue, the decomposition rates in the air and on the soil surface were similar, but both were less than the decomposition rates below the ground. The sheaths always decomposed at a lower rate than the other two tissues at any position. During decomposition, the N concentrations for all tissues decreased at both the aerial and the surficial positions but increased for belowground leaves and sheaths in the last months. For the N amount, these three tissues generally exhibited a net N release during the experiment irrespective of the position. Overall, position plays a crucial role in controlling early-stage litter decomposition in croplands, and this role will be modified by litter quality. Therefore, further studies on litter decomposition should fully consider the litter position to comprehensively evaluate the biogeochemical cycles in agroecosystems.     

Leaf litter decomposition and soil microarthropods affected by sulphur dioxide fallout

A field experiment was set up in northeastern Italy to investigate the effects of sulphur dioxide fallout on leaf litter decomposition rates and soil microarthropods. The pollution fallout, which affected part of the Po River delta, originated from the activity of an oil-fired power plant located at Isola Camerini (Porto Tolle, Rovigo). Four sampling sites, exposed to different amounts of pollutant fallout, were selected along the river bank. Two sites, located 1·5 km from the power-plant stack, received minimum sulphur dioxide fallout and were used as controls; two high-deposition sites were about 13 km away from the power-plant settlement. Soil cores were taken to compare sulphur concentrations in the upper layers of the sampling site soil profiles. Litter bags filled with plant material of various types, laid down over two consecutive sampling periods, were used to study leaf litter decomposition and sulphur accumulation on plant tissues. Microarthropods were extracted from the litter bags by means of a modified Tullgren apparatus. Soil chemical analysis showed the highest sulphur concentrations at the high pollutant deposition sites along the plume path. Litter bag dry weight loss over time was reduced by sulphur accumulation in plant tissues. Sulphur accumulation in litter bags gave an indirect measure of the differential pollutant deposition over the land. High-deposition sampling sites showed a significant reduction in the total number of some decomposers. Collembola, in particular, appeared to be a robust bio-indicator of pollutant fallout. Conclusions were drawn about the possible detrimental effects of sulphur compounds on soil and leaf chemistry, litter decomposition and microarthropod decomposer populations.© 1997 John Wiley & Sons, Ltd.     

文献三峡库区森林植被林地枯落物现存量及其持水能力

 基于三峡库区森林资源2类清查数据,结合森林植被林地枯落物现存量样地调查及浸泡实验,建立关于浸泡时间的持水量和吸水速率系列预测模型,对库区主要森林植被类型林地枯落物现存量及持水特性进行研究。结果表明:1)三峡库区不同植被类型林地枯落物现存量在一些类型间存在显著差异——杉木林林地枯落物现存量最高,达到11.610 t/hm²;柏木林枯落物现存量最低,仅为3.948t/hm²。2)不同森林植被类型林地枯落物的含水率竹林最高,达到182.9%,柏木林枯落物含水率最低,仅为32.2%。3)所有森林植被类型林地枯落物持水量均随浸泡时间的延长而增大,24h后增加速度急剧下降,48h后基本达到饱和;竹林枯落物的饱和持水量最高,达到自身质量的3.367倍,灌木林最低,为2.089倍。4)不同森林植被类型林地枯落物在前2h内吸水速度最大,类型间差别也较大,之后急剧下降,20 h后类型间吸水速度趋向一致,48h后基本不再吸收水分。5)三峡库区不同森林植被林地枯落物现存量干质量总量为2 048万5 668 t,枯落物对单场次降水的潜在持水总量为4 695万3 451t,现实饱和持水总量为3 291万7 480t。单位面积林地枯落物潜在持水量和现实饱和持水量的空间分布体现"东高西低,南高北低"的特征。研究结果可为科学评价森林植被水源涵养功能奠定基础,也可为三峡库区林业生态工程规划与建设提供理论依据。     

Microbial biomass dynamics during the decomposition of leaf litter of poplar and eucalyptus in a sandy loam

Soil microbiological properties during decomposition of leaf litter of poplar (Populus deltoides) and eucalyptus (Eucalyptus tereticornis) were studied under laboratory conditions. Microbial biomass C and ninhydrin-N were measured at different intervals up to 90 days following incorporation of poplar and eucalyptus leaves separately @ 20 and 100t ha^-1. In general, the net increase in total biomass C or ninhydrin N following amendment was larger in the soils which received poplar leaves than in the soils that received eucalyptus leaves. The amounts of biomass C, at day 90, in the soils which received eucalyptus leaves @ 20 and 100 t ha^-1 was about half and one-third, respectively, that of the soils that received poplar leaves at the same rates. Similarly, the field soils naturally receiving eucalyptus leaf litter contained about half the amounts of biomass C or ninhydrin N of the soils that received poplar leaf litter. In contrast, the amounts of organic C and total N were more in soils which received eucalyptus leaves both in the laboratory experiment and under field conditions than in the soils that received poplar leaves, indicating that the decomposition of eucalyptus leaves in soils was slower than that of poplar leaves. The ratio of biomass C/soil organic C in soils receiving eucalyptus leaves was about 2–4 times lower than those in soils with no admendment or soils receiving poplar leaves. These results, therefore, suggest that the allelochemicals released into soil during decomposition of eucalyptus leaves had a toxic effect on soil microorganisms and may thus affect the nutrient cycling and hence soil fertility.     

Water soluble elements in decomposing japanese cedar needle litter

Many studies on the decrease in the contents of elements of decomposing litter have been carried out usually by applying the litter bag method in forest ecosystems. Release of elements from the litter, however, can be divided into three routes, that is, via liquid, solid, and gaseous phases, including leaching, fragmentation, and decomposer respiration, respectively. This study focused on water soluble elements in the decomposing needle litter of Japanese cedar (Cryptomeria japonica, D. Don) as a route of release via the liquid phase. Because rainfall leaches water soluble elements from decomposing litter on forest floor, the leaching process is important for the transport of elements from litter layers to soil horizons, which can affect the composition of soil solutions (Takahashi 1995). Moreover, nutrients in the leachate can be used for microbial and plant communities to control the dynamics of these communities. I investigated 1) the relationships between water soluble elements and the decomposition stages of the litter, and 2) variation in the contents of water soluble elements.