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。     

模拟凋落物添加与氮磷沉降对红松凋落物生态化学计量特征的影响

[目的]探究红松(Pinus koraiensis)凋落物和氮(N)磷(P)沉降量、小气候因子、降水化学成分和地形对各层凋落物生态化学计量的影响,为红松林管理提供科学依据.[方法]本研究对阔叶红松混交林(天然林)和红松纯林(人工林)进行了为期712天的原位观测试验,模拟氮磷沉降与凋落物添加处理后,测定不同凋落物层次和林...     

我国热带亚热带森林凋落物及其对土壤的影响

本文研究了我国热带、亚热带森林凋落物的数量、化学组成、分解速率及其土壤发育特点。研究表明,季雨林的凋落物量 > 雨林 > 常绿阔叶林;凋落物中灰分总量以季雨林的最大、雨林的次之,阔叶林最少;凋落物的分解速率以最初的90天内最快,以后渐趋缓慢,凋落物在地表的分解速率比表土层快10-20%。热带亚热带森林有明显地生物富集作用,通过凋落物不断增加土壤有机质、提高土壤肥力,改善土壤结构。凋落物归还给土壤的养分元素总量为0.305-1.123吨/公顷·年。由此可以判断土壤发育进程的快慢,如季雨林土壤的发育进程相刘较快,雨林次之,常绿阔叶林最慢。     

杉木凋落物及其生物炭对土壤微生物群落结构的影响

以福建建瓯万木林自然保护区内的杉木人工林土壤为研究对象,设置单独添加生物炭、单独添加凋落物以及混合添加凋落物和生物炭处理,进行一年的室内培养实验,研究不同添加物处理对土壤性质及微生物群落结构的影响。结果表明:与对照(S)相比,单独添加凋落物与混合添加凋落物和生物炭均使土壤磷脂脂肪酸(PLFA)总量、真菌丰度以及真菌/细菌比值显著增加;单独添加生物炭与混合添加凋落物和生物炭均使革兰氏阳性细菌/革兰氏阴性细菌比值显著增加。混合添加凋落物和生物炭处理的放线菌丰度显著高于单独添加凋落物处理的。主成分分析表明,不同添加物处理的土壤微生物群落结构存在显著差异;典范对应分析表明,不同添加物处理通过改变土壤p H、全碳、全氮、C/N、可溶性有机碳(DOC)和可溶性有机氮(DON)等性质,进而影响土壤微生物群落结构。     

滨海沙地不同人工林凋落物现存量及其持水特性

为了研究滨海沙地沿海防护林凋落物水源涵养功能,采用野外调查和室内浸泡相结合,对滨海沙地4种典型人工林(木麻黄林、湿地松林、尾巨桉林和纹荚相思林)不同分解阶段的凋落物现存量、持水率、持水量和吸水速率进行研究。结果表明:相同林龄的4种人工林凋落物现存量表现为木麻黄林(19.12 t/hm~2)湿地松林(17.51 t/hm~2)尾巨桉林(10.90 t/hm~2)纹荚相思林(10.13 t/hm~2),半分解层凋落物储量占比高于未分解层;4种人工林最大持水率在140.55%～206.47%,为尾巨桉林纹荚相思林木麻黄林湿地松林,最大持水量在20.75～30.85 t/hm~2,为木麻黄林湿地松林尾巨桉林纹荚相思林,4种人工林凋落物最大持水率和最大持水量均为半分解层大于未分解层,不同分解阶段凋落物持水率和持水量与浸水时间呈对数关系;4种人工林不同分解阶段凋落物平均吸水速率在前0.25 h内差异较大,未分解层中尾巨桉林最大为2.05 mm/h,半分解层中湿地松林最大为4.32 mm/h,不同分解阶段凋落物吸水速率与浸水时间均存在幂函数关系;凋落物有效拦蓄深为木麻黄林(2.45 mm)湿地松林(2.04 mm)尾巨桉林(1.87 mm)纹荚相思林(1.72 mm)。综合来看,木麻黄林凋落物的持水能力最强,湿地松林次之,之后是尾巨桉林和纹荚相思林,说明从凋落物水源涵养能力来看,木麻黄林和湿地松林更利于滨海沙地的水源涵养。     

坡耕地土壤结皮形成的影响因素分析

以天然降雨侵蚀特征为依据 ,在室内研究了坡耕地土壤结皮的形成特征。通过对结皮坚实度、容重和厚度的测定发现 ,在结皮的形成过程中 ,降雨以打击夯实作用为主 ,径流以淤积压实作用占主导地位 ,且随雨强、径流深度的增加 ,这种作用也愈加显著 ;但随坡度增大 ,两者的作用受到了抑制 ,使结皮形成的完善程度降低。总体来看 ,降雨的作用要大于径流作用     

凋落物对土壤呼吸的贡献研究进展

土壤呼吸是土壤碳库输出的主要途径,凋落物是影响土壤呼吸的重要因素。明确凋落物对土壤呼吸的贡献,有助于准确评估植物-土壤-大气三个碳库之间的碳收支过程。本文综述了近年来国内外有关凋落物对土壤呼吸贡献的研究成果,阐明了凋落物对土壤呼吸的贡献机理,讨论了凋落物对土壤呼吸贡献率及其存在的时空分异特征,在此基础上,对该领域研究前景进行了展望。     

黄土区坡耕地土壤结皮对入渗的影响

黄土高原地区,坡面土壤水分是生态建设的关键问题。以黄土高原坡耕地人为管理方式为背景,在室内人工模拟降雨条件下采用等高耕作和人工掏挖两种措施,并且设计直线坡作为对照,研究不同耕作措施下土壤结皮的形成特征,同时从降雨-入渗的角度研究两种类型结皮(结构结皮和沉积结皮)对坡面土壤水分入渗的影响。研究结果表明:土壤结皮阻碍坡面土壤水分入渗,结皮坡面产流时间早,且土壤累积入渗量明显低于无结皮坡面;采用Kostiakov模型、Horton模型、蒋定生模型对坡面土壤水分入渗过程进行优化模拟的结果表明蒋定生模型适用于描述本研究坡面土壤水分入渗的特征;耕作措施造成的微地形对土壤结皮的类型有很大影响,在洼地径流携带泥沙堆积形成沉积结皮,地势较高处降雨雨滴直接打击形成结构结皮。研究两种类型结皮发现,沉积结皮相对于结构结皮密度高且孔隙度低,并且两种类型结皮对坡面土壤水分入渗的影响存在差异,沉积结皮平均减渗效应为37.13%,结构结皮平均减渗效应为19.79%,因此,沉积结皮更大程度影响坡面土壤水分入渗。     

凋落物中次生代谢物对森林土壤可溶性氮的影响

通过外加性质不同的凋落物以及不同浓度的单宁酸,于武夷山不同海拔高度的森林土壤中进行培养,研究森林凋落物中次生代谢物对土壤可溶性氮(N)的影响。结果显示,土壤经加入凋落物处理,其可溶性N含量降低。加入杉木凋落物使红壤可溶性N含量降低12.0%～27.5%,杉木较竹叶凋落物处理降低作用显著(p0.05);对黄红壤添加不同浓度单宁酸处理显示,与对照比较,高浓度单宁酸可显著(p0.001)降低土壤可溶性N含量,降低幅度在40.6%～48.1%,而低浓度单宁酸对土壤可溶性N的影响不显著。表明植物凋落物,尤其是杉木对土壤可溶性N的影响很可能与其本身单宁酸含量差异有关,从而影响了土壤可溶性有机N和无机N的转化。     

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.     

黄土结皮的发育机理与侵蚀效应研究

了解土壤结皮的发育特征及其对侵蚀的影响作用,是认识土壤侵蚀机理、建立精准侵蚀预报模型的重要理论支持之一。本文通过模拟降雨试验,探讨有无雨滴打击作用下黄土结皮的发育过程以及前期有无结皮时结皮侵蚀效应的动态特征。结果表明:(1)随降雨的进行,黄土结皮发生层容重、抗剪强度(含水率为20%)不断增加,30min内形成厚度约3～4mm稳定结皮层;(2)消除雨滴打击后,黄土结皮发育过程同有雨滴打击时类似,但程度减弱。雨滴打击同湿润作用对黄土结皮形成的贡献作用基本相当;(3)降雨初期有、无结皮处理抗剪强度差别大,随后急剧下降并趋同,因而黄土结皮影响抗蚀性的作用微弱,累积溅蚀量的差异主要由溅蚀起始时间的变化引起;(4)黄土结皮的存在明显的减少入渗、增加径流,但结皮效应随降雨进行逐渐消失。溅蚀效应的函数表达式为C=0.6670ln(t)-3.2459,结合溅蚀量的计算式,可较为准确地预测前期无结皮时某降雨历时的累积溅蚀量。     

Effects of soil invertebrates on the survival of some genetically engineered bacteria in leaf litter and soil

Seven bacterial strains, most of them bearing natural or recombinant plasmids, were introduced in oak leaf litter or soddy-podzolic soil. In these substrata, which contained litter-dwelling diplopods and isopods, or endogenic earthworms, bacteria survival was followed. In the absence of the animals, the numbers of introduced strains gradually decreased. In the presence of the animals, plasmid-bearing strains of Pseudomonas putida survived at 10⁵–10⁷ CFUs g^-1 up to 1.5 months in both leaves and soil. The total numbers of bacteria found in excrements from the soil macrofauna were 5–15 times higher than in the food. The numbers of P. putida in the excrements were equal to or higher than in the food. The numbers of Pseudomonas stutzeri JM302 (pLV1013) and Azospirillum brasiliense ATCC29710 (pFACII) in the excrements were always 2–10 times lower than in the food. The digestive fluid taken from the middle part of the gut of the diplopod Pachyiulus flavipes showed a strong antibacterial activity. Those bacteria with lower survival in the gut appeared to be more sensitive to digestion by the midgut fluid. In contrast, the hindgut fluid did not suppress the viability of P. stutzeri JM302 (pLV1013). We postulate that the introduced bacteria partially survive the midgut passage and then multiply with a high growth rate in the hindgut of the animals. The environmental consequences of the interactions between soil invertebrates and the released bacteria are discussed.Dedicated to Professor J. C. G. Ottow on the occasion of his 60th birthday     

Effects of soil crust and crop on runoff and erosion in Loess Plateau

Soil crust formed after rainfall has a strong influence on soil erosion, water use, and crop growth on sloping farmland. To study the effect of soil crust on sloping farmland on runoff amount and erosion sediment yield, the soil crust on sloping farmland has been studied in this paper for plantings of corn, soybeans, millet, and winter wheat. Using an outdoor rainfall simulator, the influence of soil crust on runoff rate and sediment yield on sloping farmland covered by crops has been observed. The results revealed that soil crust thickness was increased after rainfall and soil crust coverage showed little change after rainfall. Soil crust had a significant impact on runoff and sediment yield on sloping farmland. Slopes with soil crust showed higher runoff rate and less soil loss than slopes without soil crust. On slopes planted with four crops (corn, soybeans, millet, and winter wheat), runoff rates on slopes with soil crust were respectively 20%, 25%, 25%, and 21% higher than on slopes without soil crust; sediment yield on slopes with soil crust was respectively 15%, 14%, 14%, and 8% lower than on slopes without soil crust. Crops enlarged the runoff difference between the two kinds of slope and decreased the sediment yield difference between them. Crop growth enhanced these differences in runoff and sediment yield between slopes with and without soil crust.     

侵蚀条件下生物结皮对坡面土壤碳氮的影响

 为了探讨侵蚀条件下生物结皮对坡面土壤碳氮的影响,通过野外小区对比试验与室内分析相结合,研究有、无生物结皮坡面土壤有机质、全氮、硝态氮和铵态氮的分布特征。结果表明：生物结皮对坡面土壤碳氮积累具有重要意义,同一坡位下,土壤有机质、全氮和硝态氮含量在0～20cm剖面上均明显表现为生物结皮大于无结皮。总体来看,生物结皮对土壤碳氮的影响主要集中在0～10cm土层,与无结皮相比,土壤有机质、全氮、硝态氮和铵态氮平均储量分别增加了44.7%、18.2%、39.2%和4.33%。生物结皮能显著增加0～2和2～5cm土壤硝态氮含量（P<0.05）,这除了生物结皮对土壤养分的保蓄效应外,还可能与生物结皮向土壤释放硝态氮有关。由于铵态氮流失特征不同于硝态氮,加之生物结皮可能会利用或释放铵态氮,使生物结皮对其影响表现出无明显规律性。相关分析表明,土壤有机质与全氮、硝态氮和铵态氮均达到了极显著或显著的正相关关系（P<0.01或P<0.05）。综上所述,侵蚀环境下生物结皮发挥着重要的固土蓄肥功能,这对研究区退化生态系统的恢复和重建具有积极的意义。     

Biological soil crust and surface soil properties in different vegetation types of Horqin Sand Land,China

Physical and chemical properties (including coverage, thickness, hardness, moisture, particle size distribution, organic matter and nutrient contents etc.) of biological soil crust and 0–5.0 cm surface soil under the crust in three types of vegetation (semi-shrub Artemisia frigida, shrub Salix gordejevii and tree Populus simonii) were surveyed in 2005 and 2006 in Horqin Sand Land to understand the effects of different vegetation types on development of soil crust and surface soil properties under crust. The results showed that 1) no physical soil crust or biological soil crust (BSC) formed on mobile dunes without vegetation, though most ground surface in originally mobile dunes had been covered by BSC fifteen years after planted vegetation was established; 2) BSC development was best in shrub S. gordejevii sites, second in semi-shrub A. frigida sites, and weakest in tree P. simonii sites; 3) development of BSC was better in moss crust distributed mainly beneath or near plant canopies than in lichen crust distributed mainly between plant canopies in all three vegetation types; 4) surface soil properties 0–5.0 cm under BSC were improved significantly in all three vegetation types compared to those in mobile sand land. The magnitude of improvement was greater in S. gordejevii sites than in A. frigida and P. simonii sites, and greater in moss crust sites than lichen crust sites, but the magnitude of improvement decreased significantly with increasing surface soil depth; 5) based on the above-mentioned results, we suggest that S. gordejevii should be favored in future planting in Horqin Sand Land.     

模拟降雨条件下土壤结皮的发展和聚丙烯酰胺对黄土上结皮形成的影响

This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.     

极端干旱区咸水滴灌林地盐结皮对土壤蒸发的影响

由于长期使用高矿化度咸水滴灌,土壤盐结皮在塔里木沙漠公路防护林带内广泛发育,它会对林带土壤蒸发过程产生重要影响。采用田间取样分析和微型蒸发器（MLS）人工控制试验相结合,分别研究了一个灌溉周期内盐结皮影响下林间裸地和防护林带内的土壤蒸发过程。结果表明,土壤水分蒸发量自表层向下层逐渐减少,且有盐结皮的土壤蒸发量小于无盐结皮土壤;土壤日蒸发量随着含水量的降低而逐渐减小,有盐结皮土壤前期高于对照,而后期低于对照;土壤累积蒸发量随着时间的变化逐渐增大,但增加量逐渐减小,有盐结皮土壤累积蒸发量小于对照;盐结皮对土壤蒸发的抑制效率随着时间的变化而不断降低,但裸地的降低速度高于林地;盐结皮抑制土壤水分蒸发的效果明显。     

陕北水蚀风蚀交错区两种生物结皮对土壤饱和导水率的影响

该文以陕北水蚀风蚀交错区普遍发育的地表和地上两种生物结皮为研究对象，分别以3种非生物结皮（无结皮、物理结皮、去除生物结皮）为对照，使用盘式入渗仪测定其饱和导水率。结果表明：与无结皮土壤相比，两种类型生物结皮均可极显著降低土壤饱和导水率；与去除生物结皮土壤相比，两种类型生物结皮对土壤饱和导水率的降低均不显著；与有物理结皮发育的土壤相比，地表生物结皮对土壤饱和导水率的降低不显著，而地上生物结皮对土壤饱和导水率的降低显著。一方面，两种生物结皮对土壤饱和导水率均有明显降低作用，预示生物结皮在降雨活动中可能会增加径流、降低入渗，阻碍研究区水分亏缺条件下的植被恢复和生态与环境建设。另一方面，与不同的对照相比，生物结皮对土壤饱和导水率的影响截然不同，该结论可在一定程度上解释当前有关生物结皮影响土壤水分入渗方面所存在的分歧。     

Incidence of soil surface crust types in semi-arid Niger

Soil water availability is most essential in the Sahelian agriculture but is hampered by several factors. Surface crusts or crust-like surfaces, which are characteristic of most Sahelian soils, have been shown to decrease water infiltrability and increase runoff. Their type and structure are influenced by soil texture, vegetation cover, erosion and deposition effects of wind and water. A soil and terrain survey in semi-arid SW-Niger was carried out to explain the patterns of soil surface crusts and the deterioration of the land. The soil surface crusts were shown to depend also on specific terrain factors including land use type and intensity, and terrain type and position. Chemical and physical soil factors such as organic carbon, soil colour and texture occurring with specific crusts indicate soil degradation, especially in sloping terrain, which increases runoff and soil erosion. For sandy soils, surface tillage is required to break up the crusts. Higher surface organic matter is recommended to enhance water infiltration in soils.     

Poultry litter and tillage influences on corn production and soil nutrients in a Kentucky silt loam soil

Broiler chicken (Gallus gallus) manure, a rich source of plant nutrients, is generated in large quantities in southeastern USA where many row crops, such as corn (Zea mays L.), are also extensively grown. However, the use of broiler manure as an economical alternative source of nutrients for corn production has not been extensively explored in this region. This study was conducted to examine the use of broiler litter as a source of nutrients for corn production, as influenced by tillage and litter rate, and any residual effects following application. In addition, the consequence of litter application to soil test nutrient levels, particularly P, Zn and Cu, was explored. The treatments consisted of two rates of broiler litter application, 11 and 22 Mg ha⁻¹ on a wet weight basis, and one rate of chemical fertilizer applied under no-till and conventional tillage systems. Treatments were replicated three times in a randomized complete block design. Corn was grown with broiler litter and inorganic fertilizer applied to the same plots each year from 1998 to 2001. In 2002 and 2003, corn was planted no-till, but only N fertilizer was applied in order to make use of other residual litter nutrients. Soil samples were taken yearly in the spring prior to litter application and 4 years after the cessation of litter application to evaluate the status of the residual nutrients in soil. Two years out of the 4-year experiment, broiler litter application produced significantly greater corn grain yield than equivalent chemical fertilizer application and produced similar grain yield in the other 2 years. Corn grain yield was significantly greater under no-till in 1999, but significantly greater under conventional-till in 2000, and no difference between the two tillage systems were observed in 1998 and 2001. With 4 years of litter application, Mehlich-3 P increased from an initial 18 mg kg⁻¹ to 156 mg kg⁻¹ with 11 Mg ha⁻¹ litter and to 257 mg kg⁻¹ with 22 Mg ha⁻¹ litter. For every 6 kg ha⁻¹ of P applied in poultry litter Mehlich-3 P was increased by 1 mg kg⁻¹. Modest increases in Mehlich-3 Cu and Zn did not result in phytotoxic levels. This study indicated that an optimum rate of broiler litter as a primary fertilizer at 11 Mg ha⁻¹ applied in 4 consecutive years on a silt loam soil produced corn grain yields similar to chemical fertilizer under both no-till and conventional tillage systems and kept soil test P, Cu and Zn levels below values considered to be harmful to surface water quality or the crop.