固沙林采伐迹地撂荒后自然恢复的植物多样性、生物量与土壤养分含量的变化

采用样方法对辽宁章古台地区樟子松固沙林采伐迹地撂荒后1～5 年内自然恢复植被组成及多样性特征进行了定位研究.结果表明:采伐迹地自然恢复形成的自然植被群落共有49种植物,分属于26个科,以菊科和禾本科植物最为丰富.1 年、2 年、3 年和5 年采伐迹地植物群落的Simpson多样性指数分别为0.681、0.792、0.845和0.870,Shannon-Wiener信息统计指数、Pielou均匀度指数的变化趋势与Simpson优势度指数基本相似.5年后植被总生物量由1.351 t·hm-2增加到9.745 t·hm-2，撂荒2年时植被系统开始产生枯落物.随着植被恢复时间增加，死地被物生物量从恢复2年时的0.824 t·hm-2增加到5年时的1.403 t·hm-2.与采伐前相比，撂荒使采伐迹地土壤表层（0～15 cm）有机质含量和土壤各层的养分含量明显增加.撂荒具有较早归还凋落物和增加土壤养分的能力.     

刈割频度对普通野生稻实验种群的影响

本文通过考察普通野生稻(Oryza rufipogon)实验种群对不同频度刈割的反应,揭示刈割对该种群的密度、株高、生物量、单枝生物量和有性生殖份额等有明显的抑制作用,对累积株高增长和光合系统份额则有一定的促进作用。刈割频度越大,作用越大。但对后两者的促进是以消耗地下部分的物质和能量为前提的,超过一定频度的刈割不仅可使其有性生殖份额降至零,还可导致种群消亡。提示过频破坏普遍野生稻地上部分是该种部分种群发生地方性绝灭的重要原因之一。     

红马蹄草的生态生物学特征及其扦插繁殖

为了解红马蹄草(Hydrocotyle nepalensis Hook.)的生态生物学特征, 对其形态解剖特征及光合特性进行了研究。结果表明, 红马蹄草叶片较薄, 栅栏组织不发达, 海绵组织与栅栏组织厚度之比较大;遮荫条件下叶片的净光合速率日变化呈单峰型, 具有较低的光补偿点、光饱和点、叶绿素a/b 以及较高的表观量子效率、总叶绿素含量、叶绿素b 含量, 这显示其耐荫特性, 对弱光环境的适应能力和利用弱光的能力较强。同时, 红马蹄草扦插繁殖迅速, 成活率较高, 以荫蔽潮湿的生长环境为佳。因此, 红马蹄草适合生长在弱光环境中, 因其具有较高的观赏价值, 是一种值得大力推广的地被植物。     

采伐干扰对帽儿山地区天然次生林土壤表层温度空间异质性的影响

研究了不同强度采伐干扰对土壤表层（3～5 cm）温度空间异质性和空间格局的影响.在帽儿山地区天然次生林内,设置3块不同强度采伐干扰处理样地: A（对照）、B（按基面积的50%随机采伐）和C（皆伐）,分别布设不同空间距离 (0.5～56 m)的取样点160、154和154个,比较了干扰以后2年内春季和夏季（共4次）土壤表层温度的空间异质性和空间格局特征.结果表明,森林采伐后,土壤表层平均温度显著增加（相差0.6～4.2 ℃,P＜0.001）,与干扰强度存在一定程度正相关,温度波动范围加大.采伐干扰导致土壤表层温度空间异质性程度和变异尺度增加,并随干扰强度加大而增大,小尺度上的空间异质性也出现增加现象,但土壤温度空间变异尺度主要体现在＜20 m范围内,空间异质性组成受干扰影响较小.经Kriging法对土壤表层温度空间格局模拟,发现采伐干扰样地土壤表层温度的空间格局强度较对照林地大,温度等值线密集,其差异春季比夏季明显.采伐干扰样地的年际间相同季节土壤表层温度格局较相似,而对照样地则呈较均匀的分布格局.     

The Technological Multiplicity of the Acheulean of the Southern Iberian Peninsula

The Acheulean of the southern Iberian Peninsula is markedly similar to the north African Acheulean. However, the characteristics of the stone tool assemblages are heterogeneous and represent complex cultural phenomena. From MIS 15, the lithic assemblages in fluvial (Guadiana, Guadalquivir and Guadalete rivers), fluvio-lacustrine (Solana del Zamborino) and karstic (Cueva del Ángel, Bolomor, Cueva Negra del río Quípar, Cueva Horá and Santa Ana) contexts exhibit analogies and technical differences representative of a phenomenon of multiplicity. Contributing to this phenomenon is the perception of technological stasis or conservatism of the Acheulean technocomplex and the different technical responses articulated by hominins to achieve equivalent results. These equivalences generate the uniformity that allows us to recognise typologies of large cutting tools (LCTs) regardless of the lithic materials used or the organisational structures of the operational sequences. These diversified typologies include handaxes, picks, and cleavers, which maintain a consistent presence despite innovations such as the Levallois flaking method. In some cases, the presence of cleavers and spheroids affects the range of represented typologies. Beneath the uniformity of the handaxes, lie organisational differences in the operational sequences. The changes and differences in the use of flakes to shape handaxes, the representation of cleavers and diversification of shaped-tool typologies all suggest differential cultural behaviours linked in part to divergent contexts. These aspects indicate that this multiplicity is related to diffusion, adaptation and cultural changes produced at the margins of the conservatism of this technocomplex. Observed changes could indicate inter-group cultural replacements, most of which retained a similar techno-typological diversity to that seen in the north African Acheulean until MIS 5. Cyclical climate change during the Middle Pleistocene affected the Strait of Gibraltar, regulating its function and conditioning the circulation of hominins and affecting cultural interactions between southern Iberian groups.     

西江坪常绿阔叶林地表径流的研究

本文采用固定小区径流法,对常绿阔叶林及其皆伐迹地草坡地表径流进行了对比研究,结果表明:常绿阔叶林年径流量为9.79毫米,占大气降水量0.5％;较迹地草坡减少径流56.3％。径流的季节变化以夏、春、秋、冬依次递减;其中4—8月为径流高峰期,径流量占全年62.4—96.5％。常绿阔叶林对暴雨以下雨量级的削减作用显著;而对持续性大暴雨以上雨量级的削减作用不明显。     

Population Development and Influence of Bursaphelenchus xylophilus on Gliocladium virens

Gliocladium virens was isolated from slash pine trees symptomatic and asymptomatic for pine wilt disease with frequencies of 24% and 10%, respectively. Populations of Bursaphelenchus xylophilus, the nematode incitant of this disease, reproduced on this fungus and inhibited its growth. Growth inhibition of the fungus was characterized by an absence of sporulation and by the formation of chains of dark, thick-walled, chlamydospore-like cells. Population increase during a 12-day period following infestation of cultures of the fungus with 10,000 nematodes averaged 3-fold at 16 C, 9-fold at 20 C, and 24-fold at 24 C. In greenhouse studies, nematode recovery from slash pine seedlings coinoculated with both organisms was significantly greater than that obtained from seedlings inoculated with the nematode alone.     

Management of below-ground biomass of <Emphasis Type="Italic">Typha angustifolia</Emphasis> by harvesting shoots above the water surface on different summer days

A dynamic model of regrowth in Typha angustifolia after cutting shoots above the water surface was formulated by characterizing the phenology and mobilization of resources from below-ground to above-ground organs after the cutting. The model parameters were determined by two cutting experiments to investigate the different strategies with flowering and non-flowering shoots after cutting in 2001 and by four cutting experiments to elucidate the regrowth characteristics after cutting on different days from June to September in 2002. A difference was evident both for flowering and non-flowering shoots and for each cutting day. From June to August, non-flowering shoots regrew immediately after cutting, but flowering shoots did not. The shoot regrowth height, number of leaves and shoot biomass were higher with the earlier cutting. The model was validated using the below-ground biomass observed in December 2002 and below-ground dynamics observed in 2003. In the low-flowering shoot zone of the stands, in which the percentage of flowering shoots was small (around 10%), the decrease in below-ground biomass became larger from June (20%) to August (60%). Cutting the high-flowering shoot zone (flowering shoots: 78%) in July 2001, just 1 week after peduncle formation, decreased the below-ground biomass by about 50%. In the low-flowering shoot zone, cutting just before senescence is better for decreasing below-ground biomass with a smaller rate of flowering shoots. The difference of below-ground biomass reduction in non-flowering shoots is mainly due to the decrease in downward translocation (DWT) of above-ground material to below-ground organs during senescence, because of the decrease in regrowth biomass. As for flowering shoots, the decrease in the photosynthate transportation from above-ground to below-ground organs and that of DWT are closely related because they cannot grow again within the season.     

长江三峡地区典型灌丛的生物量及其再生能力

 灌丛是三峡地区典型的退化生态系统类型。本文采用收获法和模拟砍伐实验研究了三峡地区铁仔灌丛、椎木灌丛、荆条灌丛和黄栌灌丛的生物量及黄栌灌丛、椎木灌丛地上部分砍伐后的再生能力。研究结果表明,这4种类型的灌丛总生物量分别为22.5±5.1、21.0±3.7、16.9±7.5和13.6±2.4t·hm-2,相当于同纬度地带性生态系统常绿阔叶林(30年林龄)的10％一25％ 4种灌丛灌木层占总生物量、地上部分生物量和地下部分生物量的90％以上。在生物量—物种序列中,前5种植物占总生物量的84％ 以上。不同地点灌丛生物量的比较表明,同一种类型灌丛,亚热带和暖温带地区总生物量没有明显差异。通过模拟砍伐实验,黄栌灌丛、被木灌丛地上部分全部砍伐后1年地上部分生物量就可以恢复到对照的42.7％和62.0％,说明这些灌丛类型具较高的生长速度和很大的恢复潜力。     

Accumulation of buried seeds and establishment of ruderal therophytic communities in disturbed habitat,central Japan

The establishment and maintenance mechanisms of pioneer communities were investigated in ruderal habitats under two disturbance regimes, frequent and infrequent cutting sites. In the infrequent cutting sites, large perennials dominated through the year and inhibited the invasion of annuals, and the perennial community succeeded to forest stage if the cutting was stopped. In the frequent cutting sites, therophytic communities of winter and summer annuals alternated by season. Fresh seeds of both winter and summer annuals are dormant, but they have different germination times and thus can share the same sites in different seasons. Wind-dispersed biennials and large perennials have nondormant seeds and easily invade the sites; however, they are unable to mature to reproductive phase due to recurrent cuttings. The therophytic species, which can complete their life-cycle in a period between cuttings, accumulate seeds in the soils and are maintained by these buried seeds (seed bank annuals) during recurrent disturbances. The seed bank is compensation for the dispersal inefficiency of seed bank annuals. After abandonment of the frequent cutting sites, the buried seeds of seed bank annuals germinate and become the first-year pioneers. Thus, seed bank annuals are not invasive colonizers but are the remnants of the ruderal weed communities before abandonment.