高山森林林窗对凋落物分解过程中水溶性氮和磷的影响

采用凋落物分解袋法,以川西高山森林典型乔木(四川红杉Larix mastersiana、岷江冷杉Abies faxoniana、红桦Betula albo-sinensis和方枝柏Sabina saltuaria)和灌木(高山杜鹃Rhododendron lapponicum和康定柳Salix paraplesia)凋落物为研究对象,研究林窗中心-林下不同生境(林窗中心、林冠林缘、扩展林缘和林下)在第1年分解的不同关键时期(雪被形成期、雪被覆盖期、雪被融化期和生长季节)凋落物水溶性氮和磷的动态特征。结果表明:经过1年的分解,6树种凋落物水溶性氮含量表现为在冬季降低,但是在生长季节显著增加的变化趋势,而水溶性磷含量总体上呈现降低的变化趋势。相对于林窗中心,雪被形成期凋落物水溶性氮含量在扩展林缘和林下显著增加,但雪被覆盖期水溶性氮和磷含量均在林窗中心达到最大值。尽管凋落物水溶性氮含量在雪被融化期达到整个时期同一林窗生境下的最低值,但凋落物水溶性磷含量从林窗中心到林下逐渐降低。生长季节6树种凋落物水溶性氮含量显著增加,甚至高于初始含量,但水溶性磷含量持续降低,且水溶性氮和磷在林窗中心和林冠林缘含量较大。相关分析表明,高山森林凋落物分解第1年水溶性氮含量与正积温和冻融循环次数均呈显著负相关,而水溶性磷含量与日均温、正积温和负积温均呈显著负相关,与冻融循环次数均呈显著正相关,同时物种显著影响凋落物分解过程中水溶性氮和磷含量。这些结果表明,气候变暖情景下高山森林冬季林内雪被厚度降低,将显著影响雪被形成期和覆盖期凋落物水溶性氮和磷分解,进而影响生长季节凋落物分解。     

西藏原始暗针叶林凋落物有机碳释放特征与土壤有机碳库关系研究

结合野外凋落物分解袋法和室内分析试验,对藏东南2种典型暗针叶林—急尖长苞冷杉(Abies georgei var.Smithii)和林芝云杉(Picea likiangensis var.linzhiensis)凋落物的分解和有机碳释放特征进行研究,分析了2种亚高山暗针叶林凋落物有机碳释放速率与土壤有机碳及其组分之间的关系。结果表明:藏东南2种原始暗针叶林凋落物分解均呈现出雨季分解快(4—9月)、旱季分解慢(10—翌年3月),前期分解快(3—9月)、后期分解慢(10—翌年2月)的特征,且冷杉(PLLF)分解速率大于云杉(AGSF),Olson指数衰减模型能够较好地模拟2种暗针叶林凋落物的分解,冷杉(PLLF)和云杉(AGSF)凋落物半分解时间为2.11,2.52年;分解95%时间为8.96,10.84年;2种暗针叶林凋落物中有机碳含量表现出先上升后下降,再平稳降低的趋势,而2种暗针叶林凋落物中有机碳释放速率表现出先短暂富集再释放的模式;2种暗针叶林土壤总有机碳(TOC)及其活性组分(MBC、POC、LOC)含量都具有明显的表聚性(p<0.01),且同一土壤层次内TOC、MBC、POC、LOC互相之间均呈极显著正相关关系(p<0.01);2种暗针叶林凋落物分解进程中有机碳的释放速率与表层土(0—10 cm)中TOC、MBC、POC、LOC含量、10—20 cm土层中的TOC、MBC含量以及20—40 cm土层中MBC含量之间呈现显著的正相关(p<0.05)。     

采煤沉陷区沙柳和小叶杨凋落物分解特征比较

[目的] 探究采煤沉陷区生态修复植物凋落物的分解特征及影响因素,为干旱气候条件下采煤沉陷区的生态修复提供理论依据。[方法] 采用野外分解袋试验的方法,选取沙柳(Salix psammophila)、小叶杨(Populus simonii)和沙柳与小叶杨混合凋落物3个处理,研究分析了在风沙土和黄土基质条件下,3种类型凋落物分解1 a后的残留量、有机碳(OC)、氮(N)、磷(P)、酸性洗涤纤维(ADF)和酸性洗涤木质素(ADL)的含量变化。[结果] ①沙柳凋落物年分解速率比小叶杨和混合凋落物高10%～15%;凋落物在黄土上的分解速率比在风沙土上的速率高13%～23%。②凋落物树种对凋落物OC,N和P含量有极显著(p＜0.01)影响,土壤类型对OC,N,P,ADF和ADL的含量均有显著(p＜0.05)或极显著(p＜0.01)影响,表明树种和分解土壤基质均是影响凋落物养分转化的重要因素。③不同凋落物处理之间,沙柳凋落物的OC,N含量高于混合和小叶杨,而沙柳凋落物的P含量在分解试验前4个月低于小叶杨和混合凋落物,随后接近该值。[结论] 相比沙柳,小叶杨凋落物分解较慢,在土壤上形成覆盖能够保持更长时,更适合作为内蒙古采煤沉陷区主要的修复植物。     

不同间伐强度下天然次生林凋落物分解进程研究

以辽宁东部地区天然次生林的典型林型-柞树为主的杂木林为研究对象,在不同间伐强度的杂木林内采取埋置分解袋并定期观测的方法研究林分凋落物的分解规律。观测结果表明:辽东天然次生林凋落物分解过程存在着明显的季节变化,可划分为4个时期;用Olson指数衰减模型拟合了凋落物分解的年度变化动态,凋落物在刚凋落的前3年分解迅速,分解率50%以上。3年以后分解速率明显下降;杂木林内凋落物分解速度随间伐强度的增大而减小,间伐后湿度变小是主要原因;凋落物分解速度和林分凋落量的动态消长过程决定凋落物贮量和土壤养分状况,弱度间伐林分和未间伐林分凋落物贮量、表层土壤有机质含量明显高于中度间伐林分和强度间伐林分。     

茂兰喀斯特森林自然保护区凋落叶分解动态

[目的]研究喀斯特森林生态系统凋落叶分解特征,为喀斯特森林区石漠化防治及水土保持提供科学依据。[方法]采用1 mm网孔孔径分解袋,对茂兰喀斯特森林自然保护区不同树种凋落叶(落叶和常绿叶)在不同坡位的分解状况进行为期18个月的观测研究。研究茂兰喀斯特森林自然保护区凋落叶失重率和干重残留率动态变化、分解速率及养分释放特征。[结果]凋落叶分解过程呈现"快—慢—快"的周期变化,春夏季分解速度快于秋冬季,落叶树种凋落叶分解速度快于常绿树种凋落叶,不同坡位凋落叶的分解速度表现为:下坡中坡上坡。利用Olson模型对凋落叶分解50%和95%所需时间进行估测,发现落叶树种凋落叶分解50%和95%所需时间分别为0.95～1.66 a和4.13～7.19 a,常绿树种凋落叶分解50%和95%所需时间分别为1.14～1.69 a和4.92～7.30 a,二者无显著性差异。凋落叶分解速率低于中亚热带东部常绿阔叶林和常绿落叶阔叶混交林,但比同区域喀斯特次生林与人工林高。落叶树种凋落叶和常绿树种凋落叶的N元素释放模式为富集—释放模式,C含量随分解时间的波动差异显著,总体在不断减少,而C/N比呈逐步下降的趋势。[结论]由于不同树种凋落叶初始养分含量和叶片理化结构的差异,落叶比常绿叶具有更快的分解速率和养分释放速率,对促进喀斯特森林生态系统物质循环起着积极作用。     

甘肃省兴隆山森林主要树种凋落叶分解速率与初始质量的关系

[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。     

亚热带地区3种喀斯特林分凋落物组成对其持水性能的影响

[目的] 揭示亚热带不同喀斯特林分凋落物组成对其持水性能的影响，为丰富森林生态水文研究和加深凋落物层与水文功能关系的认识提供科学依据。 [方法] 收集亚热带喀斯特区的青冈林、青冈+光蜡树林、化香树+密花树林3种代表性林分的凋落物层，将其分为半分解、未分解枝、未分解叶和其他未分解凋落物4种成分，选择每种林分前3种主要成分分别按0%，20%，40%，60%，80%和100%比例混合成21组质量相同、组成比例不同的处理(3种林分共63组处理)。采用浸水法研究其持水性能。 [结果] ①3种林分类型不同组成凋落物的持水率和吸水速率分别与浸水时间呈对数函数关系(R²≥0.718)和幂函数关系(R²≥0.998)；在各浸水时段的持水率和吸水速率以化香树+密花树林纯未分解叶凋落物最大，青冈+光蜡树林纯未分解枝凋落物最小； ②凋落物的持水率和吸水速率均与未分解叶比例呈极显著正相关关系(p＜0.01)，与未分解枝的比例呈极显著负相关关系(p＜0.01)，与半分解凋落物的比例无明显关系； ③3种林分类型凋落物层的总蓄积量及其最大持水量无显著差异，但青冈林凋落物层的最大吸水速率显著高于化香树+密花树林。 [结论] 凋落物组成显著影响其持水性能。在凋落物生态水文效应研究中应综合考虑凋落物蓄积量及其组成的影响。     

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。     

岷江上游两种亚高山林分枯落物层水文特征研究

研究对比了岷江上游岷江冷杉林和川滇高山栎林枯落物层的水文特征,结果表明,川滇高山栎林凋落呈现多峰型,凋落高峰出现在6月,8月和10月;而岷江冷杉林凋落则为双峰型,凋落高峰出现在10月份和1月份.川滇高山栎林的枯落物未分解层、半分解层和已分解层的现存量分别为4.00 t/hm2.6.77 t/hm2和14.43t/hm2;而岷江冷杉林的枯落物未分解层、半分解层和已分解层的现存量分别为1.14 t/hm2,7.40 t/hm2.11.99t/hm2.川滇高山栎林和岷江冷杉林枯落物总最大持水量为分别为(60.23±11.82)t/hm2和(66.79±24.05)t/hm2.两种森林群落类型枯落物持水量(mm)与浸水时间(h)呈较好的对数函数关系.枯落物未分解层、半分解层和已分解层的持水量与浸水时间之间均呈极显著相关(p<0.001).     

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。     

百里杜鹃景区马缨杜鹃林凋落物对土壤蒸发的影响

[目的]探究百里杜鹃景区马缨杜鹃林下凋落物覆盖对土壤蒸发的影响,为其林下水源涵养功能的发挥提供科学依据。[方法]根据土壤蒸发理论,采用自制微型蒸渗装置进行模拟试验,参照百里杜鹃林下凋落物现存状况,研究不同质量相同比例及相同质量不同比例的凋落物覆盖对土壤蒸发抑制的影响。[结果]不同分解程度凋落覆盖比例相同质量不同时,土壤水分蒸发量随凋落物的质量增大而减小;土壤水分蒸发量随着土壤含水率的下降呈递减关系,当含水率每下降0.5%时,60,30和15 g凋落物覆盖的土壤水分蒸发量分别依次减少了0.11,0.49和1.23 g。凋落物覆盖质量相同时,不同分解程度的凋落物对土壤水分蒸发抑制作用不同,表现为:未分解半分解已分解。[结论]凋落物覆盖量越多,对土壤蒸发的抑制作用越大;凋落物分解程度越低,对土壤蒸发的抑制作用越好。     

Effects of mixing radiata pine needles and understory litters on decomposition and nutrients release

A microcosm experiment was conducted to understand the impacts of mixing radiata pine (Pinus radiata D. Don) needle litter and understory (gorse—Ulex europaeus L., broom—Cytisus scoparius L., bracken—Pteridium aquilinum L., and lotus—Lotus pedunculatus L.) litter materials on decomposition and nutrient release dynamics. Mixing of pine needle litter with understory litter material had significant impacts on both the rate of decomposition and nutrient release patterns of pine litter as well as that of the understory species. Incubation in microcosms over 10 months resulted in significantly lower mass loss of radiata pine needle litter mixed with broom and lotus litters (35.8±8.4 and 41.3±0.8%, respectively) than pure pine needle litter (63.5±2.3%). Mixing with pine needle litter significantly increased the mass loss of broom (53.1±6.1%) compared to that of pure broom (30.2±1.0%). Significant transfers of nutrients, especially of magnesium and potassium, were observed in litter mixture treatments. Concentration of K in litter materials was found to be the most limiting factor for the decomposing microorganisms in the present study. The findings of this study suggest that management of understory litter composition via weed control could be used to manipulate carbon turnover and nutrient release in the forest floor. Also, initial selection of understory species will be important and could be managed.     

Litter-fall and litter decomposition in a low Mediterranean shrubland

Annual production of litter by Cistus incanus (L.) and Myrtus communis (L.) and decomposition dynamics of leaf litter of these species was studied in a Mediterranean shrubland. Myrtus and Cistus produced 472 and 429 g dry weight litter m^-2 year^-1, respectively. Leaves were the predominant litter component for both species. The average decay constant of Myrtus and Cistus litters enclosed in litter bags, calculated over the whole study period (38 months), was 0.71 year^-1 and 0.31 year^-1 respectively. In green leaves the N content differed during growth seasons for both species, whereas the content of Ca, Mg, P, K, and Na did not show significant changes. Abscised leaves had lower N, P and K contents than green leaves, evidencing that a nutrient translocation before abscission occurred from senescent leaves. The nutrient contents of the leaves at abscission time, generally higher in Cistus than in Myrtus, allowed us to estimate the annual nutrient input to the soil. Phosphorus and K more than N were rapidly released by the decomposing litters after exposure. Nutrient limitation, in particular P, might be considered the main growth limiting factor for Myrtus and Cistus. Both species were adapted to recovery and rapidly recycle P more than N and K in the living biomass through retranslocation from green leaves before abscission and/or a high release rate from the decomposing litter. The former strategy was better used by Cistus, the latter by Myrtus.     

太岳山不同郁闭度油松人工林枯落物及土壤水文效应

通过定位试验结合室内测定的方法,研究了山西太岳山不同郁闭度油松人工林枯落物及土壤水文效应。结果表明:(1)不同郁闭度林分枯落物储量变化范围为7.43~10.86t/hm2,随郁闭度增加枯落物储量增加;最大持水率变化范围为276.54%~311.33%,最大持水深为8.02~14.34mm,表现为(按郁闭度排序):0.70.60.80.5,郁闭度为0.7林分的枯落物持水效果最好;枯落物未分解层和半分解层持水量与浸泡时间呈明显对数关系(R0.87),持水速率与浸泡时间呈明显幂函数关系(R0.94)。(2)不同郁闭度林分土壤容重变化范围为1.36~1.49g/cm3,总孔隙度均值变化范围为44.71%~48.75%,有效持水量变化范围为395.33~831.00t/hm2,表现为(按郁闭度排序):0.60.70.50.8;稳渗速率变化范围为1.00~3.47mm/min。     

森林凋落物分解研究进展

 森林凋落物分解是森林生态系统养分生物循环的重要环节,而分解过程中所释放的CO2是全球碳素收支的重要组分,开展森林凋落物分解研究是充分认识森林生态系统结构和功能的基础。研究认为:凋落物分解的预测指标可分为3类,即环境指标(如实际蒸散量)、凋落物物理质量(如叶抗张强度)和化学质量指标(如C/N比、木质素/N比和C/P比等);凋落物分解过程中养分释放机制极其复杂,养分动态模式主要有淋溶—释放、淋溶—富集—释放和富集—释放3种,并因凋落物种类、分解阶段和元素本身性质的不同而异;凋落物混合分解并非单一树种分解的简单叠加,因树种组成和比例不同,基质的化学组成会发生变化,从而影响分解者的多样性、丰富度和生理活性,进而直接和间接地影响其分解速率;凋落物混合分解中可能存在无效应、促进效应和抑制效应;现有的研究结果显示,凋落物混合分解的适宜比例应与群落中不同树种的种群比例相一致;CO2浓度升高不仅影响凋落物的化学性质,而且与分解环境中土壤的生物活性密切相关,但CO2浓度升高并不改变凋落物质量与分解速率之间的关系;越来越多的研究显示,CO2浓度升高的环境下,植物群落的物种组成会产生变化,这种变化对养分循环速率的影响远大于单纯大气CO2浓度变化的影响。     

Seasonal distribution of Xenylla brevispina (Collembola) in the canopy and soil habitat of a Cryptomeria japonica plantation

We investigated the life cycle and habitat use of an arboreal collembolan species, Xenylla brevispina, in the canopy and soil of a conifer (Cryptomeria japonica D. Don) plantation. The adaptive significance of migration between arboreal and soil habitats in the maintenance of its population in relation to the vertical structure of the forest is discussed. We sampled dead branches with foliage in the canopy (canopy litter) and on the forest-floor (soil litter). X. brevispina had one generation a year throughout the 3 years of the study. The mean densities of X. brevispina were similar in the canopy litter (0.06 to 14.57 g⁻¹ dry weight) and the soil litter (0.44 to 18.99 g⁻¹ dry weight). Seasonal patterns of density and relative abundance indicate that individuals of X. brevispina in the canopy were closely associated with those in the soil. These results suggest that vertical migration between the canopy and the soil might be a strategy allowing X. brevispina to be a predominant collembolan species in this forest.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

Effect of litter quality on its decomposition in broadleaf and coniferous forest

Recently there has been much interest in the effect of litter mixing as well as the effect of different forest habitats on the decomposition process. Our aim was to test two hypotheses: high quality litter promotes decomposition of poor quality litter, and litter decomposes faster in broadleaf than in coniferous forest. We conducted a litter mixing experiment using litterbags placed in two forest floors, in which treatments consisted of litter monocultures of each of two campy species (Castanopsis eyrei and Pinus massoniana), as well as mixtures of these two species. The results showed that C. eyrei leaves decomposed significantly faster in the coniferous habitat than in their native habitat. On the other hand, P. massoniana needles decomposed significantly faster in their native coniferous habitat than in the broadleaf habitat. In our experiment we found that the mixture had different effect on different quality litter. P. massoniana needles (poor quality) had a positive effect on the decomposition of C. eyrei leaves (high quality), while C. eyrei leaves had a negative effect on the decomposition of P. massoniana needles in the mixture case in both broadleaf and coniferous habitats. The diversity of the fungi identified from different litters varied among treatments and the mass loss was positively correlated with the Shannon–Weaver diversity index of fungi. It is suggested that fungi may be one of the major drivers to control the decomposition process.     

Interactions between litter quality, decomposition and soil fertility: a laboratory study

Leaf litters from beech (Fagus sylvatica L.) and oak (Quercus robur L.) trees were collected from mixed, deciduous woodlands growing on three soil types that varied in mineral nutrient concentrations and N mineralisation potential. Litter quality, including %N, %Mn, %P, acid detergent fibre, cellulose, Klason lignin, phenylpropanoid constituents of lignin, hexose and pentose sugar (mainly from hemicelluloses) varied within species according to soil type. However, oak and beech showed the opposite responses to soil nutrient status for most of these variables. The litters were incubated in the laboratory for 12 months (at 18 °C and constant moisture) on beds of forest floor material from two soils of contrasting high nutrient material (HNM) or low nutrient material (LNM) nutrient status to investigate litter quality and substrate interactions. At 4, 8 and 12 months there were significant differences in mass losses from oak and beech litters from all sites, and for each litter type exposed to the HNM and LMN soils. At 12 months mean mass losses were higher for HNM treatment (38.7% oak, 27.8% beech) than for the LNM treatment (30.6% oak, 25.5% beech). However, the beech and oak litters from the different sites consistently responded in opposite ways on the same soil treatment reflecting site-related effects on litter quality. Initial concentration of Klason lignin was the best predictor for mass losses from litter species and litter types. Intra-specific variation in rates of litter decomposition of beech and oak litters from different sites, and differences in their interactions with the two forest floor materials, illustrate the complexities of proximate controls on decomposition that are often masked in system-level studies.