川中人工纯柏林凋落物分解动态研究

对柏木人工纯林的渊落物有机碳和一些营养元素的分解和释放过程的研究表明,柏木凋落物中有机碳和营养元素的矿化非常缓慢,凋落物有机碳的半减期是33周,氮素矿化半减期是433周,磷矿化半减期是10周,钾矿化半减期是24周,钙矿化半减期是86周,镁矿化半减期是12周。柏木早期生长缓慢、成林困难主要是受氮素不足的制约。在林分改造和营林中适当增加阔叶速生树种,改善凋落物性质．对促进凋落物分解和养分周转、改善土壤养分状况、提高柏木人工林的生态和经济效益是很必要的。     

Nurse sow strategies in the domestic pig: II. Consequences for piglet growth,suckling behaviour and sow nursing behaviour

Nurse sow strategies are used to manage large litters on commercial pig farms. However, new-born piglets transferred to nurse sows in late lactation might be compromised in terms of growth and survival. We investigated the effects of two nurse sow strategies on piglet growth, suckling behaviour and sow nursing behaviour. At 1-day post-farrowing, the four heaviest piglets from large litters were transferred to a nurse sow either 21 (1STEP21, n=9 litters) or 7 (2STEP7, n=10 litters) days into lactation. The remainder of the litter remained with their mother and was either kept intact (remain intact (RI), n=10 litters) or had some piglets cross-fostered to equalise birth weights (remain equalised (RE), n=9 litters). The 7-day-old piglets from 2STEP7 were transferred onto a sow 21 days into lactation (2STEP21, n=10 litters). The growth of new-born piglets on 1STEP21 and 2STEP7 nurse sows was initially lower than in RI litters (F_3,33.8=4.61; P<0.01), but weaning weights did not significantly differ (F_4,32.7=0.78; P>0.5). After the 1^st week of lactation, the weights and growth rates did not differ between treatments. Fighting behaviour during nursing bouts decreased over time. The frequency of fights was higher in 1STEP21 and 2STEP21 litters compared with RI litters (t₁₂₂=3.06 and t₁₂₃=3.00, respectively, P<0.05). The 2STEP21 litters had shorter nursing bouts than RI and 1STEP21 litters (t₁₀₇=−2.81 and t_81.7=2.8, respectively, P<0.05), which were more frequently terminated by 2STEP21 than RI sows (t₅₉₅=2.93; P<0.05). Transferring heaviest piglets from RI and RE litters to nurse sows reduced the percentage of teat changes during nursing bouts (RI: F_1,275=16.61; RE: F_1,308=43.59; P<0.001). In conclusion, nurse sow strategies do not appear to compromise piglet growth. However, new-born piglets transferred onto sows in late lactation experienced more competition at the udder, suggesting that the sows’ stage of lactation is of importance to how achievable nurse sow strategies are. Thus, the two-step nurse sow strategy is likely the best option (in relation to growth and suckling behaviour), as it minimises the difference between piglet age and sow stage of lactation.     

Involvement of lignocellulolytic enzymes in the decomposition of leaf litter in a subtropical forest

The involvement of ligninolytic and cellulolytic enzymes, such as laccase, lignin peroxidase, manganese peroxidase, carboxymethylcellulase (CMCase), and filter paper activity (FPA), in the decomposition process of leaf litter driven by 6 soil-inhabiting fungi imperfecti was studied under solid-state fermentations. All the tested fungi exhibited varied production profiles of lignocellulolytic enzymes and each caused different losses in total organic matter (TOM) during decomposition. Based on the results, the 6 fungi could be divided into 2 functional groups: Group 1 includes Alternaria sp., Penicillium sp., Acremonium sp., and Trichoderma sp., and Group 2 includes Pestalotiopsis sp. and Aspergillus fumigatus. Group 1, with higher CMCase and FPA activities, showed a higher decomposition rate than the fungi of Group 2 over the first 16 d, and thereafter the cellulolytic activities and decomposition rate slowed down. Group 2 showed the maximum and significantly higher CMCase and FPA activities than those of the Group 1 fungi during the later days. This, combined with the much higher laccase activity, produced a synergistic reaction that led to a much faster average mass loss rate. These results suggest that the fungi of Group 1 are efficient decomposers of cellulose and that the fungi of Group 2 are efficient decomposers of lignocellulose. During cultivation, Pestalotiopsis sp. produced an appreciable amount of laccase activity (0.56+/-0.09 U/ml) without the addition of inducers and caused a loss in TOM of 38.2%+/-3.0%, suggesting that it has high potential to be a new efficient laccase-producing fungus.     

红松阔叶混交林凋落物-土壤动物-土壤系统中N、P、K的动态特征

根据对小兴安岭凉水国家级自然保护区红松阔叶混交林的凋落物、土壤动物和土壤2a的连续采样及测定主要营养元素N、P、K的含量,研究凋落物-土壤动物-土壤系统中主要营养元素在各分室的动态变化,并通过比较主要营养元素在不同分室中的分异,进而分析了土壤动物在该系统营养循环中的作用。结果表明,研究区内不同凋落叶分解过程中元素含量的动态变化比较复杂,阔叶落叶中营养元素含量的变化大于针叶落叶,但不同凋落叶在分解过程中的元素损失量之间的差异不显著。在研究时段,腐殖土层各种营养元素的含量高于土壤层;蚯蚓、蜈蚣和马陆大型土壤动物体内的营养元素含量之间差别较大,其中蚯蚓体内全N含量最高,而马陆体内全P含量最高,蜈蚣则全K含量最高。土壤动物和土壤中营养元素含量的动态变化和凋落叶中的变化趋势不同。N和P在土壤动物分室中表现出一定的富集,而K的富集不明显。土壤动物可以通过其新陈代谢活动加速凋落物-土壤动物-土壤系统中营养元素的循环速率。不同凋落物分解过程中养分含量变化复杂可能是由于不同凋落物种类特性差异造成的。土壤动物在营养元素循环,尤其是N、P元素循环中具有重要意义。     

杉木叶片内生真菌定殖对凋落物分解及其微生物活性的影响

【背景】植物内生真菌在植物组织由衰亡转入腐生过程中发挥重要的作用,但这种作用可能因植物及其内生真菌种类不同而具有差异。【目的】分析不同优势度种类内生真菌定殖对于凋落物分解及其相应微生物活性的影响。【方法】采用凋落物分解袋法,选取优势树种杉木凋落叶作为分解底物。【结果】不同优势度类型的内生真菌单菌或组合定殖在分解过程前期几乎均显著加速了凋落物分解,而在分解后期,除了Irpex lacteus和Colletotrichum sp.,这种加速效应几乎均在减弱,甚至抑制了分解过程。微生物活性各变量对内生真菌定殖处理的响应与失重率并不完全一致,这依赖于分解时期。CO2释放速率在前期与失重率相关性不强,而后期则密切相关;分解前期羧甲基纤维素酶(carboxymethylcellulase,Cx酶)对失重率贡献较大,然而后期漆酶与过氧化物酶对失重率的贡献升高。总之,内生真菌定殖对凋落物分解及相应的微生物活性均产生了较大影响。【结论】对内生真菌定殖效应的研究有助于人们对森林生态系统土壤碳库平衡和养分循环维持机制的理解,同时对于贫瘠人工林土壤肥力的恢复研究也具有重要的意义。     

桉-桤不同混合比例凋落物分解过程中 土壤动物群落动态

采用凋落物分解袋法研究了10:0(TⅠ)、7:3(TⅡ)5:5(TⅢ)、3:7(TⅣ)和0:10(TV)巨桉(Eucalyptus grandis)和台湾桤木(Alnus formosana)混合凋落物分解过程中的土壤动物群落特征.从5种类型、3种规格的810只凋落袋中共收集土壤动物75651只,隶属2门10纲20目,其中弹尾目(Collembola)和蜱螨目(Acarina)为优势类群.土壤动物个体数最高是7-8月,大型土壤动物个体数最高是7月,中小型土壤动物个体数最高是7-8月.大型、中小型土壤动物类群数各月间均波动较小.与30目和6目相比,260目网袋中弹尾目和蜱螨目等中小型土壤动物数量更高.相对台湾桤木(TV)而言,巨桉(TⅠ)凋落物中弹尾目数量更多.啮虫目(Psocoptera)在台湾桤木(TV)凋落物中的数量远远高于其它凋落物,后孔寡毛目(Opisthopora)在混合凋落物中数量较高.不同比例的凋落物混合可改变凋落物中土壤动物的数量和组成.桤木、混合凋落物中大型土壤动物的个体数高于巨桉凋落物,而且上述凋落物的分解速率亦明显快于巨桉凋落物,这意味着大型土壤动物的活动可加速凋落物的分解.因此,在巨桉人工纯林中混栽台湾桤木,可显著提高大型土壤动物的数量,促进凋落物的分解.     

外源氮素调控C/N比对杉木林凋落叶细菌群落结构的影响

为探究不同C/N比对杉木凋落叶分解特性的影响,通过添加外源氮,采用分解袋法,分析林下植被保留和林下植被去除2种林分中不同C/N比值的杉木凋落叶分解300 d时细菌群落结构差异。研究显示：一定范围内,初始C/N比降低有利于杉木凋落叶分解和细菌群落多样性提升,过低的C/N比则具有抑制作用;相比于林下植被去除,林下植被保留管理措施更有利于杉木凋落叶的分解,且细菌群落多样性更高,但当初始C/N比值为20.3时,杉木凋落叶分解所受的抑制作用更为明显;在门水平上,变形菌门、放线菌门和浮霉菌门为杉木凋落叶中主要优势种群;在属水平上,慢生根瘤菌属、嗜酸栖热菌属和Singulisphaera属在杉木凋落叶中相对丰度较高;不同处理间的杉木凋落叶细菌群落结构具有显著差异,变形菌门、放线菌门和酸杆菌门等细菌门中的多类细菌相对丰度差异显著;在门分类水平上,杉木凋落叶C/N比值与主要细菌种群相对丰度的相关性最高,C/P比值与杉木凋落叶细菌群落结构变异的相关性最高;在属水平上,杉木凋落叶全碳含量、C/N比值和全钾含量与主要细菌种群相对丰度的相关性最高,全钾含量与杉木凋落叶细菌群落结构变异的相关性最高。结果表明初始C/N比的降低改变了杉木凋落叶细菌群落结构,进而作用于杉木凋落叶的分解。     

川西高山和亚高山灌丛的地被物及土壤持水性能

线以上和干旱阳坡等环境较为恶劣的地段,生态水文效应尤为重要.以往对于该区域灌丛的研究,多集中于类型、生物量等方面,生态水文效应方面的研究基本上属于空白.通过对苔藓、枯落物和土壤的野外调查与室内实验,分析了川西高山和亚高山3种主要灌丛在不同海拔梯度的地被物及土壤持水性能,其有利于加深对长江上游高山和亚高山区灌丛水文效应的认识.研究表明：（1）3种类型中,杜鹃灌丛持水性能最强,其苔藓、枯落物和土壤0～40cm最大持水量在各海拔梯度平均为46.73、139.98 t/hm^2和2216.92t/hm^2;高山栎灌丛各海拔梯度平均为1.64、72.08 t/hm^2和2114.88 t/hm^2;橿子栎灌丛没有苔藓,枯落物和土壤0～40cm最大持水量在各海拔梯度平均为84.55 t/hm^2和2062.83 t/hm^2.（2）杜鹃灌丛苔藓蓄积量及最大持水量随海拔升高而降低;高山栎灌丛苔藓蓄积量及最大持水量先随海拔升高而增加,在3400m处达到最大,之后又降低.杜鹃灌丛苔藓最大持水率远高于高山栎灌丛.杜鹃灌丛和高山栎灌丛枯落物蓄积量及最大持水量均随海拔升高而降低;橿子栎灌丛则随海拔升高而升高.（3）3种灌丛在不同海拔随土壤深度的增加,土壤容重均显著增大,最大持水量显著下降,但毛管持水量和最小持水量仅在部分类型显著下降.土壤0～40cm最大持水量只有杜鹃灌丛随海拔升高而显著降低,其他两种不同海拔间差异不显著.     

昆明种稀毛鼠与正常鼠生长繁殖的比较

目的探讨昆明（KM）种稀毛鼠与正常鼠的生长繁殖是否有差异。方法对KM种稀毛鼠与正常鼠1～8胎进行平均胎间隔、受胎率、产仔数、初生体重、仔鼠离乳成活率等繁殖力指标及1～12周龄平均体重增长等生长指标作对比实验,将实验结果进行统计学处理。结果从第5胎起稀毛鼠的受胎率、平均胎间隔、仔鼠离乳成活率三项繁殖指标均低于正常鼠。但两者的产仔数、仔鼠初生体重及育成鼠周平均增重却无明显差异。结论平均胎间隔、平均受胎率、仔鼠离乳成活率是影响稀毛鼠正常生产的关键。     

川西亚高山桦木林的林地水文效应

川西亚高山森林是我国西南亚高山林区水源涵养林的重要组成部分,原生的亚高山暗针叶林在经历大规模采伐利用后,天然更新的次生桦木林已成为该区域的主要森林类型之一。前人对原始暗针叶林水文学的研究已相当丰富,内容涉及冠层截留、地被物持水特征、森林蒸发散、土壤入渗、根土作用层等诸多方面;而对于采伐后人工林和天然次生林的研究较少,仅有的结论也以人工林为主。通过对林地苔藓、枯落物和土壤的野外调查与室内实验,分析了川西亚高山次生桦木林在不同林龄和海拔梯度间的林地水文效应,这对于丰富亚高山森林水文学的研究、确定长江上游水源涵养林的恢复与重建模式,都具有重要的意义。研究表明:桦木林苔藓蓄积量及最大持水量在不同林龄间差异显著,随林龄增大而显著增加;而在不同海拔间差异不显著。枯落物蓄积量及最大持水量在不同林龄及海拔间均差异显著,随林龄的增大而增加;在林龄相同的条件下,在中海拔(3200m、3400m)较高,在较高(3600m)、较低(3000m)海拔偏低。苔藓最大持水率平均为945%,在林龄和海拔间差异不显著;枯落物最大持水率平均573%,在林龄和海拔间均差异显著。各林龄和海拔梯度上的桦木林,随土壤深度的增加土壤容重均显著增大,最大持水量显著下降,但毛管持水量和最小持水量仅在部分类型下降显著。土壤0~40cm最大持水量在不同林龄间差异不显著,而在不同海拔间差异显著;这种差异主要表现在林龄10~25a的林分,随海拔升高土壤0~40cm最大持水量增大。在大规模采伐后,苔藓层的恢复是一个长期过程,可以作为次生林地水文效应向原始暗针叶林恢复程度的一个指标。