山东石灰岩山地植被结构与演变

在群落调查的基础上,对山东省淄博市沂源县和博山区两处代表性的石灰岩山地植被于2001年和2005年进行2次调查,从群落物种的重要值、物种多样性、生态位等方面对山东石灰岩山地植被的现状进行了生态学分析,并将2001年作为有人为干扰情况下的植被现状,人工封育5a后的2005年作为经过人工封育的自然恢复现状,对石灰岩山地植被的演变进行了分析.结果表明:山东石灰岩山地植被的现状相对较差,群落的层次性不明显,灌草层的优势种为黄荆和结缕草,经过人工封育,灌草层的优势种并没有明显的变化,两地的植被还处于演变过程中,但没有达到演替的程度,沂源样地的情况和演变程度均要强于博山;灌草层物种多样性的变化并不一致,经过对物种多样性指数的计算,可以得出两地的Shannon-Wiener多样性指数都有所上升;物种优势度、生态位宽度和生态位重叠三者之间2001年相关关系不显著,但2005年相关关系显著,并且有从无直线相关到有直线相关,从直线相关到对数相关的变化趋势.     

The influence of timber harvest on the structure and composition of riparian forests in the Coastal Redwood region

The composition and structure of riparian forests in the coast redwood region were analyzed in relation to the length of time since timber harvest, and the width of riparian buffer zone. Ten sites were sampled in the central range of the coast redwood forest type within a variety of post-harvest age groups and riparian buffer zone widths. Data was collected using randomly selected sample plots adjacent to perennial coastal steams. Correlation Fisher's r to z tests and two-tailed t-test were used to examine the relationship between the sample variables and the experimental parameters “years since harvest”, and “width of buffer.” Results indicate that canopy cover was negatively correlated to “years since harvest” with the highest level of canopy cover found on the youngest sites and the lowest level found on the old-growth sites. The hardwood to conifer dominance ratio and the basal area of Alnus rubra (red alder) were correlated negatively to both “years since harvest” and “buffer width” indicating that timber harvest favored hardwood species. Late seral associates such as Oxalis oregana (redwood sorrel), Anthyrium filix-femina (lady fern), and Vaccinium parviflorum (billberry) were found preferentially in older forests and sites with wider buffer zones, while non-native species such as Hedera helix (English ivy), Pampas cortedaria (pampas grass), and Myosotis latifolia (forget-me-not) were found preferentially in younger forests and areas with smaller buffer zones.     

Effects of bamboo stands on seed rain and seed limitation in a rainforest

Bamboos often negatively affect tree recruitment, survival, and growth, leading to arrested tree regeneration in forested habitats. Studies so far have focused on the effects of bamboos on the performance of seedlings and saplings, but the influence of bamboos on forest dynamics may start very early in the forest regeneration process by altering seed rain patterns. We tested the prediction that the density and composition of the seed rain are altered and seed limitation is higher in stands of Guadua tagoara (B or bamboo stands), a large-sized woody bamboo native from the Brazilian Atlantic Forest, compared to forest patches without bamboos (NB or non-bamboo stands). Forty 1 m² seed traps were set in B and NB stands, and the seed rain was monitored monthly for 1 year. The seed rain was not greatly altered by the presence of bamboos: rarefied seed species richness was higher for B stands, patterns of dominance and density of seeds were similar between stands, and differences in overall composition were slight. Seed limitation, however, was greater at B stands, likely as a resulted of reduced tree density. Despite such reduced density, the presence of trees growing amidst and over the bamboos seems to play a key role in keeping the seeds falling in B stands because they serve as food sources for frugivores or simply as perches for them. The loss of such trees may lead to enhanced seed limitation, contributing ultimately to the self-perpetuating bamboo disturbance cycle.     

Effects of landscape composition and configuration on northern flying squirrels in a forest mosaic

Habitat loss and sometimes habitat fragmentation per se affect species survival, reproduction, dispersal, abundance and distribution. However, understanding the independent effects of fragmentation (i.e., landscape configuration) has been limited because it is frequently confounded with landscape composition (i.e., habitat amount). We assess the independent effects of landscape composition and configuration on the occurrence of northern flying squirrels (Glaucomys sabrinus) in New Brunswick, Canada after controlling for local site conditions. We measured landscape structure using an “organism-based” approach; landscape structure was characterized quantitatively using a spatially explicit local-scale distribution model for northern flying squirrels.     

Impact of Macrotermes termitaria as a source of heterogeneity on tree diversity and structure in a Sudanian savannah under controlled grazing and annual prescribed fire (Burkina Faso)

Macrotermes termitaria are conspicuous features of savannah ecosystems in the Sudanian and Sahelian zones of West Africa. The mounds, alive or abandoned, are a major source of heterogeneity in the landscape. The purpose of the present study was to assess the impact of termitaria on tree community in a state forest of the Sudanian regional centre (Tiogo forest, Burkina Faso), under controlled burning and grazing experiments. A comparative inventory was carried out in a split-plot experiment (16 subplots of 2500 m²): 8 subplots where fire regime and grazing were controlled and 8 subplots exposed to grazing and with annual prescribed fire since 1992. All tree individuals (≥1.5 m) were recorded, both on termitaria and outside and their basal area at stump level was measured. A total of 61 observed (or 65.7 ± 2.4 estimated) tree species were recorded on 28 Macrotermes subhyalinus mounds (54 observed species or 60.8 ± 3.3 estimated), the immediate surroundings (44 observed and 59.0 ± 0.0 estimated species) and the rest of subplots (56 observed and 63.6 ± 0.0 estimated). Specific density was higher on mounds in comparison with the surroundings (P < 0.05). Results showed that termitaria played a key role in maintaining higher species diversity as compared to their surroundings (P < 0.05). Differences in species diversity between termitaria and immediate surroundings appeared more pronounced in disturbed plots (submitted to both fire and grazing). Some species, such as Tamarindus indica, Boscia senegalensis, Cadaba farinosa, Capparis sepiaria and Maerua angolensis are found solely on termitaria. Besides, the density of trees was significantly higher on termitaria compared to the surrounding (P < 0.05), as well as total basal area per unit of 100 m² area (P < 0.05). We concluded that Macrotermes termitaria play an important role as a source of heterogeneity in this Sudanian savannah woodland ecosystem. This role is particularly important in ecosystems under stresses. Termitaria acted as refuge for tree vegetation. The density and dynamics of M. subhyalinus termitaria should, therefore, be taken into account in the global strategy of the forest resources management and conservation.     

Effects of moisture limitation on tree growth in upland and floodplain forest ecosystems in interior Alaska

The objective of this study was to examine the impact of summer throughfall on the growth of trees, at upland and floodplain locations, in the vicinity of Fairbanks, Alaska. Corrugated clear plastic covers were installed under the canopy of floodplain balsam poplar/white spruce stands and upland hardwood/white spruce stands to control soil moisture recharge as a result of summer precipitation. The covers were installed in 1989 and tree growth measurements were conducted through 2005. Soil moisture dynamics were measured using TDR techniques. Tree basal area growth at dbh in the control plots was approximately twice as high on the floodplain compared to the upland. Summer throughfall exclusion significantly decreased white spruce growth on the floodplain sites but not in the upland sites. In upland sites the melting snow pack is a major moisture resource for tree growth although it is not clear if moisture limitation occurs during the summer in the control plots. However in the floodplain stands white spruce growth was highly dependent on seasonal throughfall even though the ground water table was within the rooting zone and the soils were supplied with a spring recharge due to snowmelt. A number of factors were suggested as a foundation for this strong relationship. These include rooting distribution, soil texture, and the electrical conductivity of the ground water.     

Effects of fitch odor (Mustila eversmanni) on behavior and breeding of root voles (Microtus oeconomus)

From April to December in 1997 at Northwest Plateau Institute of Biology, Chinese Academy of Science, the effect of predation risk on social behavior, feeding, reproduction and sexual hormones of the root voles (Microtus oeconomus) was studied when the root voles (Microtus oeconomus) were exposed to the odor of fitch (Mustila eversmanni). The results showed that the root voles delayed breeding period and the frequency of the copulation significantly lowered (P<0.01). Comparing with the control group, the accumulated time of amicable behavior in females, and general activity of both sexes increased significantly (P<0.01). The frequencies of general activity (P<0.01), investigating activity (females:P<0.05, males:P<0.01), and self-grooming (P<0.01) of both sexes were less significantly. At the same time, the amount of energy intake (P<0.05) and body weight (P<0.01) of the root voles decreased significantly. The litter weight and ovary index of females decreased (P<0.01). For males the sperm count in epididymides also decreased significantly (P<0.01). The progesterone in the blood serum of root voles females increased significantly under fitch odor (P<0.01). Biography: WANG Zhen-long (1971-), male, lecture in Department of Biology, Qufu Normal University, Qufu 273165, P.R. China Responsible editor: Zhu Hong     

Sap flow measurements reveal influence of temperature and stand structure on water use of Eucalyptus regnans forests

We examined water use by maturing Eucalyptus regnans, growing with or without an mid-storey stratum of Acacia spp. (Acacia dealbata or A. melanoxylon), for >180 consecutive days. Study sites were located in the Upper Yarra catchment area in south-eastern Australia. Depending on their contribution to stand basal area, mid-storey Acacia spp. increased total stand water use by up to 30%. Monthly water use in such stands reached more than 640,000 L ha⁻¹ (compared to 545,000 L ha⁻¹ in stands where acacias were absent) in early spring. Water use was curvilinearly related to sapwood area of Acacia spp. and logistically related to sapwood area of E. regnans. Water use of all three species showed a strong relation to daily maximum air temperatures. Distinct and simple relationships provide clear guides to the likely impacts of climate change and forest management on water yield. We compared a traditional up-scaling approach, from individual tree water use to stand water use, to a new approach that incorporates variation in temperature. Development of this approach can lead to greater precision of stand water use estimates – and in turn catchment water yield – under current climate change scenarios, which predict a rise in air temperatures of 0.6–2.5 °C by 2050 for the study area. Our temperature-dependent approach suggests that under conditions of non-limiting water availability, stand water use will rise by 2% for every 0.25 °C increase in maximum air temperatures during winter, and possibly more than that during summer.     

固氮树种对第二代桉树人工林土壤微生物生物量和结构的影响

为了探究固氮树种对我国南方亚热带地区第二代桉树人工林土壤微生物生物量和结构影响及其机制,采用磷脂脂肪酸分析方法分别在干季和湿季研究了第二代桉树纯林和第二代桉树/固氮树种混交林的土壤微生物群落生物量和结构。结果表明:与纯林相比,混交林土壤(0 10 cm)的有机碳含量、铵态氮、硝态氮、总氮、凋落物生物量分别提高了17.77%、41.62%、85.59%、25.38%、19.12%,除土壤有机碳外,其它在统计学上均达到了显著性差异(p0.05);混交林的细菌生物量显著增加,但其真菌生物量显著减少;同时,混交林的总细菌、革兰氏阳性细菌相对百分含量在干季显著提高,真菌的相对百分含量却显著降低;但在湿季,除总细菌外,其它微生物群落结构没有显著差异。主成分分析(PCA)表明:第二主成分轴能明显把第二代桉树混交林和纯林的土壤微生物群落区分开来(p0.05),这种差异主要体现在混交林具有较高的细菌相对百分含量和相对较低的真菌相对百分含量。冗余度分析(RDA)表明:凋落物生物量、凋落物C/N、铵态氮、有机碳含量是驱动我国南方第二代桉树人工林土壤微生物群落结构发生变化的主要因子。此外,壕沟切根试验表明根系及其分泌物可能是第二代桉树人工林土壤微生物的重要碳源。     

Effects of overstory retention and site preparation on growth of planted white spruce seedlings in deciduous and coniferous dominated boreal plains mixedwoods

Survival and growth of planted white spruce was assessed under partial harvest treatments and different site preparation techniques in mixedwood forests of two compositions prior to logging: deciduous dominated (d-dom) – primarily comprised of mature trembling aspen (Populus tremuloides Michx.) and coniferous dominated (c-dom) – primarily comprised of mature white spruce (Picea glauca (Moench) Voss). Levels of overstory retention were 0% (clearcut), 50% and 75% of original basal area, and site preparation techniques were inverted mounding, high speed mixing, scalping and control (no treatment). The survival and growth of white spruce were assessed seven years after planting. The experiment was established as a part of the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment located in northern Alberta, Canada. In the c-dom, the 50% and 75% retention of overstory resulted in reduced growth and survival of white spruce seedlings compared to clearcuts. In contrast, in the d-dom, the seedlings performed best in sites that had 50% of the overstory retained. For the c-dom, the mounding and mixing treatments yielded the best growth of spruce seedlings, while scalping yielded the worst. In the d-dom, spruce growth was highest in sites with the mixing treatment. In the d-dom, growth and survival of the planted spruce was greater than in the c-dom. The natural regeneration of deciduous trees was suppressed by the retention of canopy regardless of original composition.     

沙丘不同部位中间锦鸡儿人工林土壤养分特性及植物群落特征

以青海共和盆地沙丘上12年生的中间锦鸡儿人工林为研究对象,并以流动沙丘为对照,探讨在沙丘上建立中间锦鸡儿人工林后,沙丘部位对土壤养分含量以及植物群落的影响。在中间锦鸡儿人工林内沙丘的迎风坡中部、坡顶、背风坡中部和流动沙丘采集土壤样品,深度为0 5,5 10,10 20和20 50 cm。结果表明:与流动沙丘相比,沙丘3个部位中间锦鸡儿人工林0 20 cm的有机质、0 50 cm的全氮和全磷含量得到显著提高。迎风坡中间锦鸡儿人工林0 5 cm深度的土壤有机质和全氮、0 20 cm深度的全磷含量显著高于坡顶和背风坡。在沙丘上建立中间锦鸡儿人工林后,草本植物种类、数量和植被盖度增加,迎风坡草本植物盖度明显高于坡顶和背风坡。     

Effects of Pinus massoniana bark extract on the adhesion and migration capabilities of HeLa cells

Pinus massoniana Lamb is a Chinese red pine species used in traditional medicine for the treatment of a variety of human health disorders. Recent studies have shown that P. massoniana bark extract (PMBE) has an anti-proliferation effect on cancer cells. However, it is not clear if PMBE affects cancer cell migration and/or invasion. We tested the effect of PMBE, which has B-type procyanidin as its main constituent, on the adhesion and migration capabilities of HeLa cells, a human cervical cancer cell line, cultured in vitro. Our results showed that PMBE has no significant effect on the adhesion capability of HeLa cells, but strongly inhibits their migration. This finding suggests that PMBE could be a potential therapeutic agent for metastatic cancer.     

Senescence of Manilkara zapota trees and implications for large frugivorous birds in the Southern Yucatan Peninsula,Mexico

It has long been established that mature forests are mosaics of patches in different development phases but it has seldom explicitly been taken into account in ecological studies. We demonstrate here that these development phases, which are related to the population dynamics of trees, play an important role in the distribution of fauna based on observations on frugivorous birds. In an area close to the Calakmul Biosphere Reserve in Mexico, we studied the abundance of large forest bird species in relation to forest development phases, with a methodology that seems promising for ecological diagnosis and prognosis in forest management planning. Fine-scale forest mapping and bird counts were carried out in two block-transects of 40 m × 3000 m. Tree sampling in a sub-transect was used to generate population characteristics of trees. Large bird species preferred mature or senescent forest patches, whereas relatively young, growing forest patches were avoided. Important large tree species such as Manilkara zapota, Thouinia paucidentata, Guaiacum sanctum and Esenbeckia pentaphylla, characteristic of older forest patches, showed skewed size distributions indicating stress or overexploitation. The population of M. zapota, a key fruiting species that accounted for 26.5% of the total woody biomass, was most heavily affected by stress. A future collapse in the population of M. zapota, a decrease of the total area of older forest, and a decline in the abundance of large birds is likely if stress on the system continues at this level.     

杉木林分蓄积生长的密度及立地效应

采用3参数Weibull生长方程,对15块杉木密度试验林26年连续观测数据进行分析,计算了林分材积年平均生长量(MAI,包括净材积年平均生长量(MAInet),总材积年平均生长量(MAIgross));利用相关分析及逐步回归分析,研究了林分净材积(Vnet)和总材积(Vgross=Vnet+枯死木材积累积(∑Vm))年平均生长量的峰值及峰值林龄与初植密度、立地质量的关系。结果表明:(1)MAInet峰值与立地指数呈显著正相关,而受林分密度影响很小,其在立地指数级22 m的样地内平均值比立地指数级12 m的样地增加了8.33 m3·hm-2·a-1;MAIgross峰值与立地质量及林分初植密度均呈正相关(r=0.813 5,p=0.000 4;r=0.926 1,p=0.000 0);(2)MAInet峰值林龄主要受初植密度的影响,初植密度太大或太小对MAInet峰值林龄有显著影响,E密度(1 m×1 m)样地的MAInet峰值林龄平均值比A密度(2 m×3 m)样地的小3.88年,而中间密度的MAInet峰值林龄变化不明显。     

水分胁迫对四倍体刺槐苗生长和光合作用的影响

刺槐是我国三北地区的主要防护造林树种,尤其是西北干旱、半干旱地区有广泛的种植;但由于当地气候条件的制约,刺槐难于获得生长所需的足够水分[1],生长受到严重抑制,在黄土高原出现了大面积的"小老树"和低劣残次林[2-4],其生态、经济效益都很低.