凋落物和土壤覆盖对动物取食和搬运辽东栎种子的影响

在六盘山区的华北落叶松人工林,研究了清除凋落物、凋落物覆盖和土壤覆盖(以不清除凋落物直接将种子投放于森林地表为对照)等处理对动物取食和搬运辽东栎种子的影响.结果表明:种子释放3d后,凋落物和土壤覆盖处理种子均具有较高的留存率(分别为10.7％和7.0％);释放14 d后,土壤覆盖处理种子的留存率仍最高(0.7％),但凋落物覆盖处理种子的留存率为0.凋落物和土壤覆盖处理种子的就地取食率很高(分别为45.9％和41.5％);清除凋落物处理种子的就地取食率最低(27.0％),但其被搬运后的取食率最高(49.8％);凋落物覆盖、清除凋落物和土壤覆盖处理种子被动物搬运后的埋藏率均显著高于对照(P＜0.01).种子被动物搬运后集中分布于5 m以内,尤其在＜1 m和l～2m两个距离组的分布频率更高;种子被搬运后取食的平均距离大干埋藏的平均距离,以土壤覆盖和凋落物覆盖处理最大,分别为2.38 m±0.55 m和1.44m±0.26 m.     

啮齿动物对六盘山区辽东栎、野李和华山松种子的取食和搬运

为了阐明不同种子投放方式和覆盖处理对啮齿动物取食和搬运/贮藏种子行为的影响,2010年春季,我们在宁夏六盘山区的辽东栎幼林,用塑料标签标记法研究了不同种子投放方式(单独投放、两两组合投放和混合投放)和覆盖处理(对照、凋落物覆盖和土壤覆盖)下啮齿动物对辽东栎、野李和华山松种子的取食和搬运特点。结果表明:(1)不同物种、不同种子投放方式和覆盖处理对种子的就地取食率、搬运后的取食率和贮藏率均具有显著影响,种子较大或具有厚而坚硬的种皮(内果皮)、组合和混合投放及覆盖处理均不同程度地促进啮齿动物对种子的搬运;(2)3种植物的种子被搬运后取食和贮藏的平均距离范围均在5.5m以内,而且种子被搬运后贮藏的距离均大于搬运后取食的距离,其中华山松种子被搬运后取食的距离显著大于辽东栎和野李种子,但搬运后的贮藏距离显著小于后两者。(3)种子被搬运后单个种子的取食点和贮藏点占多数,其他大小的取食点和贮藏点较少,种子被搬运后以土壤埋藏为主要的贮藏方式。结果表明,种子的种皮特征以及种子在群落中的分布方式和存在状态,可能通过延长啮齿动物处理的时间而增大啮齿动物的被捕食风险,使动物改变对种子的取食和搬运行为,进而决定了种子的命运。     

啮齿动物对不同大小和种皮特征种子的取食和搬运

在宁夏六盘山区的辽东栎灌丛,以不同大小的辽东栎种子、野李和华山松种子为材料,研究了种子大小和种皮特征对啮齿动物取食和搬运行为的影响.结果表明:辽东栎小种子和华山松种子的就地取食率均显著高于辽东栎大种子和野李种子;具有厚而坚硬种皮(内果皮)的野李种子被啮齿动物搬运后的取食率和贮藏率均最高.辽东栎大种子被啮齿动物搬运后取食的距离最大(3.10 m),被搬运后贮藏的距离(6.48 m)显著大于其他类型种子.除野李种子外,其他3种类型种子的单个种子取食点都在80％以上,所有种子的单个种子贮藏点都在90％以上,含2个以上种子的取食点和贮藏点较少.较高比例的华山松种子在灌丛基部和洞穴以外的其他环境被取食,其他3种类型种子被啮齿动物搬运后主要集中在灌丛基部和洞穴中取食;种皮(内果皮)厚而坚硬的种子以土壤埋藏方式贮藏的比例偏高.     

啮齿动物及凋落物存留对天山野果林野生樱桃李种子命运的影响

2010年9月至2013年4月通过设置人工土壤种子库,研究了野生樱桃李土壤种子库的动态及啮齿动物和凋落物覆盖对种子库中种子命运的影响.结果表明: 在有取食动物扰动下,48.3%的种子萌发输出为幼苗,50%的种子被动物搬运或当场取食,4%的种子腐烂.在排除了取食动物干扰的条件下,樱桃李种子形成了短期持久的土壤种子库,3年后依然有部分种子萌发并输出为幼苗.凋落物覆盖和对照处理中,被搬运和当场取食种子的比例均显著低于清除凋落物的裸地.地表凋落物存留能减少动物搬运、取食,但不足以导致新生幼苗的大量出现,而啮齿类动物的搬运或取食是影响野生樱桃李种子命运和种子库动态的主要因素.
     

六盘山区辽东栎的实生苗更新及其影响因子

研究了六盘山区辽东栎(Quercus liaotungensis)灌丛的种子产量、土壤种子库组成、湿沙和风干贮藏对种子寿命的影响以及动物取食子叶对种子萌发和幼苗建立的影响。结果表明, 辽东栎灌丛种子的完好率为27.51%, 被动物取食或搬运种子的比例(41.51%)显著高于其他类型种子(p < 0.01); 辽东栎次生林土壤种子库中萌发和虫蛀种子分别占35.16%和38.29%, 完好种子仅占13.65%, 捕食动物主要通过贮藏或搬运而影响土壤种子库中的种子密度。湿沙贮藏60天的辽东栎种子自动萌发率高达96.67%, 短期贮藏可加快种子的萌发进程, 提高萌发率和萌发指数, 但随着贮藏时间的延长, 种子萌发进程延迟, 萌发率、萌发指数和活力指数均不同程度地降低。排除动物取食处理的幼苗在林窗和林下生境的存活率分别为80%和83%, 而不排除动物取食幼苗在2种生境中分别仅有25%和31%能够存活, 表明子叶在幼苗建立中具有重要作用。林窗中幼苗子叶的动物取食率(85.00%)高于林下(71.00%), 子叶留存的幼苗在林窗中的存活率(6.00%)低于林下(15.50%), 而子叶被取食幼苗的存活率在两种环境中基本相等(分别为18.50%和18.00%)。     

鼠类对山杏和辽东栎种子的贮藏

在北京市东灵山地区,选择灌丛生境,人工释放山杏和辽东栎种子,对两种种子在释放处被鼠类就地取食、存留动态、种子被搬运和贮藏的距离、位置、状态、微生境等进行了分析比较。采用活捕饲喂和咬痕比较的方法,对野外取食山杏和辽东栎种子的鼠类进行了鉴定。结果表明：1)取食山杏和辽东栎种子的鼠类主要是大林姬鼠和岩松鼠;2)山杏种子被鼠类搬运的平均距离大于辽东栎种子,两种种子大多数被搬运至21m之内,在9m之内最为集中;3)山杏种子的中位存留时间较辽东栎种子长;4)在释放处,鼠类对辽东栎种子的就地取食强度(54．83％)大于对山杏种子的取食(0．17％);5)在搬运之后,大部分山杏种子被埋藏起来,仅有3粒被取食;而辽东栎种子大部分被取食;6)鼠类趋向于把种子搬运到灌丛下方或灌丛边缘进行贮藏或取食。山杏种子在贮藏点的数量为1—3粒,而辽东栎种子在贮藏点的数量均为1粒。     

灌丛高度对啮齿动物贮藏和扩散辽东栎坚果的影响

本文选择高、矮两类灌丛生境, 于2002 年至2003 年在其中释放标记的辽东栎坚果, 并连续记录释放坚果的命运, 以了解生境差异对啮齿动物搬运、取食和贮藏辽东栎坚果的影响以及啮齿动物对微生境的选择等。研究结果表明, 大林姬鼠等啮齿动物对辽东栎坚果的短期取食非常强烈, 而分散贮藏的量则相对较少; 啮齿动物对辽东栎坚果的搬运距离在矮灌丛生境中显著大于高灌丛生境; 啮齿动物倾向于选择灌丛边缘和灌丛下方取食或贮藏辽东栎坚果, 这类微生境也有利于埋藏坚果的萌发。     

生境类型对啮齿动物扩散和贮藏栓皮栎坚果的影响

在河南省济源市王屋山地区,研究了次生林、灌丛、退耕地三个生境中啮齿动物对栓皮栎坚果的取食、
扩散与贮藏情况。结果表明:1)在研究地区,取食栓皮栎坚果的啮齿动物主要有大林姬鼠、社鼠和黑线姬鼠;
2)在次生林中,啮齿动物对坚果的搬运速率慢于在灌丛和退耕地生境中的搬运速率;3)次生林生境中,贮藏
坚果占被扩散坚果的比例高于灌丛和退耕地,而灌丛生境中被取食坚果占被扩散种子的比例高于退耕地和次生
林;4)栓皮栎坚果的中位存留时间在三个生境间有显著性差异。研究结果提示,在人工造林时,可通过对栓皮
栎坚果进行埋藏处理,以提高种子萌发率。     

不同密度下辽东栎幼苗子叶丢失及其对幼苗存活和生长的影响

在宁夏六盘山区龙潭林区华北落叶松(Larix principis-rupprechtii )人工林的不同样带, 按6个密度梯度(3.24、2.56、1.96、1.44、1.00和0.64株·m^-2)移栽萌发生根的辽东栎(Quercus wutaishanica)幼苗, 研究了啮齿动物对幼苗子叶取食的密度效应及其对幼苗存活与生长的影响。结果表明, 辽东栎幼苗的子叶留存率随着幼苗密度的增大而减小。2个高密度处理(3.24和2.56株·m^-2)的幼苗子叶留存率分别在移栽6周和5周后稳定在最低水平, 分别为8.64%和7.81%; 而2个较低密度处理(1.44和0.64株·m^-2)的幼苗在最后一次观测时子叶留存率仍很高, 分别为44.44%和31.25%, 且二者均显著高于其他密度处理(p < 0.05)。受啮齿动物取食的影响, 在从高到低的不同密度处理下, 幼苗的主根留存率分别为64.16%、80.46%、87.23%、80.25%、69.84%和69.84%; 在1.44株·m^-2处理下, 顶芽留存率最高(25.23%), 显著大于3.24株·m^-2处理(4.19%) (p < 0.05), 其他密度处理的顶芽留存率均不足20%。子叶被动物取食的幼苗和子叶完整幼苗的最终留存率基本一致, 仅在个别密度处理的某一观测时期差异显著; 顶芽被动物取食的幼苗留存率略低于顶芽完整幼苗的留存率, 但个别密度处理完全相反; 不同类型幼苗的留存率随时间推移而上下波动, 可能与幼苗顶芽被动物取食后萌生形成新芽有关。幼苗的株高、基径、叶片数和单株叶面积均随密度的减小而略有增大, 但除株高外, 其他3个生长参数均在1.44株·m^-2处理时最大, 与子叶是否被动物取食有一定的对应关系, 即高密度下更多的幼苗丢失了供应其生长所需营养物质的子叶, 从而影响了幼苗的早期生长。研究结果不仅丰富了“负密度效应”理论和种群更新的“增补限制”理论, 也可为六盘山区退化辽东栎灌丛和辽东栎次生林的恢复及生态系统管理提供 参考。     

海南岛中部丘陵地区植被恢复过程中凋落物动态及土壤碳氮含量变化

为探究海南岛中部丘陵地区植被恢复过程中凋落物分解动态和土壤碳氮含量变化,采用时空互代法,在琼中湾岭地区同时具有经自然恢复的草丛、灌丛、次生林和人工恢复的马占相思林4种植物群落的两个山坡采用凋落物袋法进行凋落物交互分解实验。结果表明:4类型凋落物在同一样地中分解时,灌丛凋落物肖梵天花分解速率最高;同一种类凋落物在4个样地中分解时,在灌丛样地的分解率较高,而在3个自然植被样地中,分解速率为灌丛>草丛>次生林,显示随着植物群落进展演替的进程,凋落物分解速率呈现先增加后降低的趋势;马占相思凋落物和在马占相思林样地分解凋落物的分解率均低于次生林。土壤碳氮含量变化不显著,但有随植被恢复进程而增加的趋势。     

Synergistic effects of primates and dung beetles on soil seed accumulation in snow regions

This study aimed to reveal the soil seed accumulation processes for endozoochorous plants in the heavy-snowfall forests of Japan, where seed dispersal agents are few when compared to tropical forests. We assessed (1) primary seed dispersal by Japanese macaques (Macaca fuscata) by identifying dispersed seeds found in their feces, and (2) secondary seed dispersal by dung beetles by using beads (as seeds mimics) of different sizes, to quantify the frequency of seed burial and burial depths. We studied this diplochorous system in different forest types (undisturbed beech forest, conifer plantation, and secondary beech-oak forest) and during the spring and summer seasons. The key findings were as follows: (1) macaques dispersed the seeds of 11 and 14 plant species during spring and summer, respectively; (2) seeds dispersed by macaques in the spring were smaller and twice as abundant than those dispersed in the summer; (3) although no differences were observed in the amount of beads buried by beetles between seasons, all bead sizes tended to be buried in deeper soil layers in the spring than in the summer; and (4) the seed supply to the soil in undisturbed beech forest and conifer plantation was greater than the one in secondary beech-oak forest. Similar to what has been observed in tropical forests, seeds defecated by frugivorous mammals can be successfully incorporated into the underground soil seed bank through a diplochorous macaque-beetle system in temperate forests of deep snow regions.     

The size and composition of soil seed-banks in remnant patches of three structural rainforest types in North Queensland

The size and species composition of the soil seed-bank in a remnant patch of each of three structurally and floristically distinct rainforests (Complex Mesophyll Vine Forest, Complex Notophyll Vine Forest and Semi-Evergreen Vine Thicket) were assessed. Seeds of 94 species germinated from 12 surface soil samples collected from each site. All three seed-banks were composed mostly of herbs characteristic of roadsides and agricultural land, and pioneer rainforest trees and shrubs. Agglomerative classifications indicated that the seed-bank samples from each rainforest remnant had a characteristic species composition and could be distinguished reliably from seed-bank samples drawn from other sites. Seeds of species present in the standing forest were poorly represented in the seed-banks except for one long-lived pioneer tree, Dendrocnide photinophylla, at one site. The seed-bank from the seasonally dry vine thicket was significantly larger (4000 seeds m^-2) than those from the two moister sites (400–600 seeds m^-2, contained more seeds of roadside and agricultural herbs, and fewer seeds of rainforest pioneer and secondary shrubs and trees. We suggest three explanations for the different seed-bank structure observed in the seasonally dry forest site. First, with increased deciduousness in rainforests, seed-banks are increasingly subject to invasion and domination by seeds of rapidly maturing herbs. Second, long-lived seeds that germinate in canopy gaps would be less likely to accumulate under deciduous forests because they would he exposed annually to conditions suitable for germination. Third, chronic disturbance by cattle and pigs produces sites suitable for the establishment of rapidly maturing herbs, and possibly disperses their seeds into the forest.     

Litterfall production, decomposition and nutrient use efficiency varies with tropical forest types in Xishuangbanna, SW China: a 10-year study

Litterfall production, decomposition and nutrient use efficiency in three different tropical forest ecosystems in SW China were studied for 10 years. Annual mean litterfall production in tropical seasonal forest (TSF) (9.47?±?1.65 Mg ha^?1) was similar to that in man-made tropical forest (MTF) (9.23?±?1.29 Mg ha^?1) (P?>?0.05) but both were significantly lower than that in secondary tropical forest (STF) (12.96?±?1.71 Mg ha^?1) (P?<?0.05). The annual variation of litterfall was greater in TSF (17.4%, P?<?0.05) than in MTF (14.0%) or STF (13.2%). The annual mean decomposition rate of litterfall increased followed the order of MTF (2.72)?<?TSF (3.15)?<?STF (3.50) (P?<?0.05), which was not correlated with annual precipitation or annual mean temperature, but was rather related to litter quality. The nutrient use efficiency was found to be element-dependent and to vary significantly among the three forest types (P?<?0.05). These results indicate that litterfall production and decomposition rates in different tropical forest systems are related to plant species composition and are influenced strongly by coexisting species and their life stage (age) but less so by the species richness. Constructing multi-species and multistory man-made tropical forest is an effective way to enhance biological productivity and maintain soil nutrients on degraded tropical land.     

Conversion of secondary broadleaved forest into Chinese fir plantation alters litter production and potential nutrient returns

Litter production, litter standing crop, and potential nutrient return via litterfall to soil were studied during a 4-year period (January 2004–December 2007) in a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation and a secondary broadleaved forest in Hunan Province in subtropical China. Mean annual litterfall in the sampling sites varied from 358 g m⁻² in the pure plantation to 669 g m⁻² in the secondary broadleaved forest. Total litterfall followed a bimodal distribution pattern for both forests. Amount of litterfall was also related to the air temperature in both forests. During the period under this study, annual variation in the total litterfall in the pure plantation was significantly higher than that in the secondary broadleaved forest. Litterfall was markedly seasonal in the both forests. Leaf proportions of litterfall in the pure plantation and secondary broadleaved forest were 58.1 and 61.7%, respectively. Total potential nutrient returns to the soil through litterfall in the pure plantation were only 46.2% of those in the secondary broadleaved forest. Total litter standing crop was 913 and 807 g m⁻² in the pure plantation and secondary broadleaved forest, respectively. Our results confirm that conversion from a secondary broadleaved forest into a pure coniferous plantation changes the functioning of the litter system.     

Seed rain into upland plant communities in Hong Kong, China

Hong Kong is an extreme example of tropical landscape degradation, with no substantial remnants of the original forest cover and a highly impoverished disperser fauna. Seed availability is a potential limiting factor in vegetation recovery in such landscapes. To assess the quantity and quality of the seed rain of woody taxa, seed traps were placed in the major upland vegetation types: fire-maintained grassland, shrubland, and secondary forest. Within the grassland site, traps were placed under isolated trees, isolated male and female shrubs of Eurya chinensis, and in the open. Seeds were collected every 2 weeks for 2 years. The seed rain was highest under female shrubs in grassland (6455 seeds m⁻² year⁻¹), where it was almost entirely confined to their fruiting period. Next highest were isolated trees (890 seeds), followed by male isolated shrubs (611 seeds), shrubland (558 seeds), forest (129 seeds) and open grassland (47 seeds). The number of seed taxa was highest in shrubland (59), followed by isolated trees (42), forest (42), female isolated shrubs (28), male isolated shrubs (15), and open grassland (9). The seed rain differed in species composition between the forest, shrubland, and grassland sites, while the differences within the grassland site were largely in terms of quantity. Birds (particularly bulbuls, Pycnonotus spp.) are known or inferred to be the major dispersal agents for 85% of the seed taxa trapped, 99% of the total number of seeds trapped, and 99.8% of the seeds trapped in the grassland site. Few taxa and of the total seeds were dispersed by wind and no seed taxa were definitely dispersed by fruit bats. The results suggest that even in the most degraded landscape the seed rain is adequate for the development of woody vegetation cover, but that human intervention will be needed for the restoration of plant diversity.     

The role of the soil seed and seedling bank in the regeneration of diverse plant communities in the subtropical Ailao Mountains,Southwest China

We compared species composition and diversity of the soil seed and seedling banks in three secondary vegetation types (shrubland, Populus bonatii forest, Lithocarpus regrowth forest) and a primary old-growth forest in the subtropical Ailao Mountains of southwestern China to clarify the importance of seed and seedling banks for forest dynamics. The average species richness was the highest in soil samples from the shrubland (26.80 ± 1.98), and the lowest from the primary forest (9.93 ± 0.50). The density of germinable tree seeds increased from the secondary vegetation to the primary forest, and the density of shrub, forb, and graminoid seeds decreased significantly. The most abundant seedlings recorded in soil samples were light-demanding species in the shrubland and Populus bonatii forest. For ground flora, the number of shrub seedlings strongly decreased with the increase in stand age, and shade-tolerant tree seedlings tended to increase. The species similarity between the seed bank and the aboveground vegetation in all sites was low (Sørensen’s index = 0.11–0.33), however, the shrubland had higher similarity compared with the other three plant communities. In the primary forest, light-demanding woody species dominated in soil seed banks, while shade-tolerant species dominated in the overstory and the forest floor. In the primary forest, seedlings of dominant tree species were rare in the understory, and no seeds of the dominant species were found in the soil. Results indicated that the early stages of vegetation recovery should take into account the possibility of recovering soil seed bank processes. However, colonization and establishment of tree seedlings will be difficult once a primary forest is destroyed.     

Releasing Rain Forest Succession: A Case Study in the Dicranopteris linearis Fernlands of Sri Lanka

Throughout tropical moist climates, Dicranopteris linearis fernlands can develop as a result of rain forest clearance followed by frequent burning. In Sri Lanka, D. linearis fern-lands are capable of suppressing the regeneration of rain forest. Field experiments were conducted at Sinharaja Man and Biosphere Reserve, a rain forest where fernlands occupy substantial areas of the reserve boundary. The experiment's objective was to identify methods for initiating forest regeneration in fernlands dominated by D. linearis Three disturbance treatments were used to initiate seedling regeneration: clean weed, root removal, and till. We hypothesized that increasing the severity of the soil disturbance would establish vegetation with higher species richness and diversity, greater above-ground dry biomass, and higher percentage cover and seedling density. Results indicate only partial support for this hypothesis. Dry biomass was greatest in till treatments, the most severe soil disturbance. By comparison, species richness and diversity, seedling density, and percentage cover were greatest in root-removal treatments, though in many instances the differences were not significant. The study clearly demonstrated that any kind of soil disturbance can facilitate the establishment of herbs, shrubs, and trees in a fernland dominated by D. linearis. Results showed that herbs, sedges, grasses, and pioneer shrubs represented greater proportions of seedling recruits than did pioneer trees. Seedlings of primary-forest tree species were nearly nonexistent. In general, results showed that soil disturbance can play an important role in site preparation for the purpose of initiating non-fern vegetation in fernlands dominated by D. linearis.     

采伐对长白山阔叶红松林生态系统碳密度的影响

采伐对森林生态系统碳密度和固碳能力有重要的影响,且影响的程度因采伐强度和方式不同而有巨大差异。以长白山地区原始阔叶红松林在不同采伐方式、采伐强度干扰后形成的次生林为研究对象,通过对2007至2009年建立的11块1 hm2永久样地中植被层、凋落物层和土壤层碳密度在采伐前后变化特征的分析,研究了采伐强度与恢复时间对阔叶红松林生态系统碳密度的影响。结果表明:在短期内,采伐导致了植被层和土壤表层(0—20cm)碳密度值的减少,其中植被碳密度与采伐强度有显著的线性负相关关系(y=-0.9x+91.17,R2=0.626,P<0.01),而后,随着植被的恢复,生态系统碳密度增加,其中植被、土壤层碳密度呈显著线性正相关关系。根据植被碳密度与恢复时间之间的相关关系,确定以生态系统恢复、木材生产与固碳三者兼顾的合适采伐强度为30%,轮伐期为45a。     

Litterfall of tropical forested wetlands of Veracruz in the coastal floodplains of the Gulf of Mexico

Canopy productivity of five seasonally flooded forests in the central area of the Gulf of Mexico was estimated by measuring the litterfall. Productivity was estimated on a monthly basis from November 2005 to October 2006, and values ranged between 9 and 15 t ha⁻¹ yr⁻¹. A total of 57 plant species were recorded based on the litter collected. The dominant species (Pachira aquatica, Annona glabra, Hippocratea celastroides and Dalbergia brownei) were the principal litterfall producers. The contribution of two life forms was assessed: trees (including trees, shrubs and palms) and lianas (climbers, lianas and creepers). Lianas were found to be extremely productive and represented between 8 and 62% of the total litterfall at the sampled locations. Leaves contributed most to the litter, followed by branches and reproductive structures. Fruit and seed fall coincided with the rainy season, and accounted for 50–90% of the production and shedding during the flooded season. Species that released seeds during this time had their seeds dispersed by water. Flower production occurred during the dry season (March–June). Species richness did not explain litterfall productivity. The litterfall productivity of these forests is similar to that of mangrove ecosystems.