湖南城步南山的植被及其合理利用

 城步南山是我国南方规模最大的牧场,总面积138,345亩(9,223公顷)。南山地区的植被,根据生态外貌原则划分为常绿针叶林、常绿落叶阔叶混交林,落叶阔叶林,灌丛、竹丛、草丛,农作物,经济林和果园等10个主要类型。现在的草丛是森林遭受破坏的次生植被。本区在开发利用上,应以发展林业为主,实行林牧结合。山地坡度大于35˚的必须发展林业,25—34˚的坡地要林牧兼顾,小于24˚者可以发展牧业,并营造各类防护林。     

Analysis of development of a subalpineAbies stand based on the growth processes of individual trees

The progress of growth of a subalpine youngAbies veitchii andA. mariesii forest during 25 years was analyzed on the basis of measurements of the processes of height growth of about 230 trees in a quadrat where the old canopy had been completely destroyed by a typhoon in 1959. The original forest floor sapling population had consisted of trees shorter than 2 m. Saplings grew faster after the breakage of the canopy than before,A. veitchii growing faster thanA. mariesii. During the 25 years of growth, a few well developed trees exceeded 6 m in height, while others remained around only 1 m or less. Some small trees, mostlyA. veitchii died at sites of high density. A bimodality in the distribution of tree height had developed with a trough at about 2.5 m, differentiating the trees into canopy and suppressed populations. Canopy trees grew with wide variation of rates, while most of the suppressed trees showed little recent growth. No difference was found in recent growth rates between the two canopyAbies species. Differences in height growth rates among individual canopy trees were analyzed on the basis of their horizontal crown overlapping. Competition models evaluating the difference in height between trees with overlapping crowns were shown to be effective. The height growth rate of a canopy tree appeared to be controlled by both the closely grown taller trees and the local density of trees including those shorter than the subject tree.     

Expanding forests and changing growth forms of Siberian larch at the Polar Urals treeline during the 20th century

The ongoing climatic changes potentially affect plant growth and the functioning of temperature‐limited high‐altitude and high‐latitude ecosystems; the rate and magnitude of these biotic changes are, however, uncertain. The aim of this study was to reconstruct stand structure and growth forms of Larix sibirica (Ledeb.) in undisturbed forest–tundra ecotones of the remote Polar Urals on a centennial time scale. Comparisons of the current ecotone with historic photographs from the 1960s clearly document that forests have significantly expanded since then. Similarly, the analysis of forest age structure based on more than 300 trees sampled along three altitudinal gradients reaching from forests in the valleys to the tundra indicate that more than 70% of the currently upright‐growing trees are <80 years old. Because thousands of more than 500‐year‐old subfossil trees occur in the same area but tree remnants of the 15–19th century are lacking almost entirely, we conclude that the forest has been expanding upwards into the formerly tree‐free tundra during the last century by about 20–60 m in altitude. This upward shift of forests was accompanied by significant changes in tree growth forms: while 36% of the few trees that are more than 100 years old were multi‐stem tree clusters, 90% of the trees emerging after 1950 were single‐stemmed. Tree‐ring analysis of horizontal and vertical stems of multi‐stemmed larch trees showed that these trees had been growing in a creeping form since the 15th century. In the early 20th century, they started to grow upright with 5–20 stems per tree individual. The incipient vertical growth led to an abrupt tripling in radial growth and thus, in biomass production. Based on above‐ and belowground biomass measurements of 33 trees that were dug out and the mapping of tree height and diameter, we estimated that forest expansion led to a biomass increase by 40–75 t ha^?1 and a carbon accumulation of approximately 20–40 g C m^?2 yr^?1 during the last century. The forest expansion and change in growth forms coincided with significant summer warming by 0.9 °C and a doubling of winter precipitation during the 20th century. In summary, our results indicate that the ongoing climatic changes are already leaving a fingerprint on the appearance, structure, and productivity of the treeline ecotone in the Polar Urals.     

接种彩色豆马勃对模拟酸沉降下马尾松幼苗生物量的影响

外生菌根能够提高宿主植物对外界环境胁迫的抵抗力,促进植物的生长,本文试图揭示外生菌根对酸雨胁迫下马尾松生长的保护作用。本研究采用盆栽试验,共设置四个处理：酸雨对照处理（Control check (CK), 约pH值5.5）不接种,酸雨对照处理接种,酸雨pH值3.5处理不接种,酸雨pH值3.5处理接种。pH值3.5的酸雨处理降低马尾松的生物量,在试验前期降低根冠比,试验中后期则提高根冠比,在试验初期增加了叶面积,但中后期显著降低了叶面积。接种外生菌根菌有利于马尾松幼苗的生长,pH值3.5处理下接种外生菌根菌能提高马尾松幼苗的生物量,外生菌根菌对生物量分配和叶面积的影响与酸雨胁迫的影响是相反的,即外生菌根菌抵消了酸雨胁迫对马尾松的影响。     

Variability of climate–growth relationships along an elevation gradient in the Changbai Mountain, northeastern China

In order to explore climate–growth relationships at different elevations, tree-ring width chronologies of larch (Larix olgensis) were developed from three sampling sites on the northern slope of the Changbai Mountain, northeastern China. There were no consistent trends in statistical characteristics of the tree-ring chronologies along the elevation gradient, since trees in the forest interior had a complacent growth pattern. Monthly mean temperature and monthly total precipitation were used for the analysis. Correlation analysis indicated that temperatures in winter had negative correlations with tree growth (previous November, December and current March for the low-, mid- and high-elevation sites, respectively). The correlations between tree growth and June temperature varied from weakly negative at low elevations to significantly positive at high elevations. Precipitation in June of the growth year had negative relationship with the high-elevation chronology. However, high precipitation was associated with low temperature in early growing season, further supporting that temperature is a growth-limiting factor at high elevations. Our results suggest that along the elevation gradient, L. olgensis may respond in different ways to local climate change.     

Interactive effects of ozone and climate on tree growth and water use in a southern Appalachian forest in the USA

* A lack of data on responses of mature tree growth and water use to ambient ozone (O(3)) concentrations has been a major limitation in efforts to understand and model responses of forests to current and future changes in climate. * Here, hourly to seasonal patterns of stem growth and sap flow velocity were examined in mature trees from a mixed deciduous forest in eastern Tennessee (USA) to evaluate the effects of variations in ambient O(3) exposure and climate on patterns of stem growth and water use. * Ambient O(3) caused a periodic slowdown in seasonal growth patterns that was attributable in part to amplification of diurnal patterns of water loss in tree stems. This response was mediated by statistically significant increases in O(3)-induced daily sap flow and led to seasonal losses in stem growth of 30-50% for most species in a high-O(3) year. * Decreased growth and increased water use of mature forest trees under episodically high ambient O(3) concentrations suggest that O(3) will amplify the adverse effects of increasing temperatures on forest growth and forest hydrology.     

亚热带常绿阔叶林不同演替阶段土壤种子库的初步研究

 本文把四川缙云山亚热带常绿阔叶林的演替系列分成6个阶段：(1)弃耕地;(2)灌草丛;(3)马尾松林;(4)以马尾松为优势的常绿针、阔叶混交林;(5)以常绿阔叶树为优势的针、阔叶混交林;(6)常绿阔叶林。分别从每个阶段分3层采集0.5m2,l0cm厚度的5个小样地的土样,带回实验室,通过萌发法研究土壤种子库。得到如下结论：A、种子数量和物种多样性在演替早期阶段(从弃耕地到马尾松林)一般随演替发展而减少,种子数目随土层加深而降低;后期阶段(马尾松林到常绿阔叶林)种子数则大致随演替发展而增加;同一阶段各土层种子数差异不大。B、各演替阶段土壤种子库的种类组成均以草本植物为主。C、在湿度和光照比较一致的情况下,萌发种子数与温度成正相关。大多数种类的种子80%以上在实验的头六个星期内萌发。D、演替早期阶段的地上植物种类组成与土壤种子库中种类组成基本一致,演替后期阶段相关甚少。本文还讨论了土壤种子库研究的取样体积问题,以及土壤种子库在植被动态中的作用。     

Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots

Several widespread changes in the ecology of old-growth tropical forests have recently been documented for the late twentieth century, in particular an increase in stem turnover (pan-tropical), and an increase in above-ground biomass (neotropical). Whether these changes are synchronous and whether changes in growth are also occurring is not known. We analysed stand-level changes within 50 long-term monitoring plots from across South America spanning 1971-2002. We show that: (i) basal area (BA: sum of the cross-sectional areas of all trees in a plot) increased significantly over time (by 0.10 +/- 0.04 m2 ha(-1) yr(-1), mean +/- 95% CI); as did both (ii) stand-level BA growth rates (sum of the increments of BA of surviving trees and BA of new trees that recruited into a plot); and (iii) stand-level BA mortality rates (sum of the cross-sectional areas of all trees that died in a plot). Similar patterns were observed on a per-stem basis: (i) stem density (number of stems per hectare; 1 hectare is 10(4) m2) increased significantly over time (0.94 +/- 0.63 stems ha(-1) yr(-1)); as did both (ii) stem recruitment rates; and (iii) stem mortality rates. In relative terms, the pools of BA and stem density increased by 0.38 +/- 0.15% and 0.18 +/- 0.12% yr(-1), respectively. The fluxes into and out of these pools-stand-level BA growth, stand-level BA mortality, stem recruitment and stem mortality rates-increased, in relative terms, by an order of magnitude more. The gain terms (BA growth, stem recruitment) consistently exceeded the loss terms (BA loss, stem mortality) throughout the period, suggesting that whatever process is driving these changes was already acting before the plot network was established. Large long-term increases in stand-level BA growth and simultaneous increases in stand BA and stem density imply a continent-wide increase in resource availability which is increasing net primary productivity and altering forest dynamics. Continent-wide changes in incoming solar radiation, and increases in atmospheric concentrations of CO2 and air temperatures may have increased resource supply over recent decades, thus causing accelerated growth and increased dynamism across the world's largest tract of tropical forest.     

Production of Seeds and Cones and Consequences for Wood Radial Increment in Norway Spruce (Picea Abies (L.) Karst.)

Abstract

The presence of a trade–off between growth and reproduction was tested in four sites in a subalpine Norway spruce (Picea abies (L.) Karst.) forest by measuring annual stem diameter increments at breast height and seed and cone productions during the periods 1962–1985 and 1983–1990, respectively. Trees growing in forest stands near the timber line (about 1900 m above sea level) had the greatest reduction in annual stem diameter increment during mast years; while trees growing at about 1300–1500 m above sea level did not show any reduction. Trees growing at about 1700 m showed only a limited reduction. At the same elevation, trees growing within closed forest stands suffered a greater reduction in stem growth when compared with trees growing at the edge of a cutting.     

Dendroecological analysis of a longleaf pine Pinus palustris forest in Mississippi

A climate model with time varying parameters was fit to longleaf pine (Pinus palustris) tree rings collected from the proposed Harrison Research Natural Area of the De Soto National Forest in southern Mississippi. The purpose of the analysis was to determine if any unexpected disturbances had influenced the growth of the trees. Current September temperature, August rainfall and February Palmer Drought Severity Index (PDSI) were found jointly to be the best variables in the model to predict growth. August rain had a constant significant effect on growth and February PDSI was not significant except between the years 1968–1983. It was concluded that the Harrison area has been in equilibrium for the past 50 years since no apparent outside influences have caused the trees to become less sensitive to climate. Thus, the forest is a good candidate for a Research Natural Area.Abbreviations (RNA) Research Natural Area     

Response of tree-ring width to climate warming and selective logging in larch forests of the Mongolian Altai

Aims The Mongolian Altai is an old settlement area, which is populated by pastoral nomads since 2000–3000 years. Forests in this region (at ca. 2300 m a.s.l.) are highly fragmented and border on steppe and alpine grasslands, which are used for mobile livestock husbandry. The climate in Central Asia is warming to levels clearly above the global average, which affects the vegetation. Furthermore, the transition from planned to market economy and the decollectivization of livestock 20 years ago has strongly changed land use practices in Mongolia, especially resulting in an increase in recent logging activities. We were interested in the question how climate warming and selective logging influence the annual stem growth and the stand structure.Methods The impact of climate and land use by the pastoral nomads on the annual stem increment of more than 1800 trees of Siberian larch (Larix sibirica) was analyzed. Different groups of trees with divergent growth trends depending on the social position and stand history were identified by non-metric multidimensional scaling and analysis of similarities. Long-term trends in the annual stem increment were analyzed by establishing separate regional growth curves for trees of different age classes.Important findings Instrumental climate data substantiate an increase of temperature by 2.1°C since 1940 at constant precipitation. Trees benefit from the increased temperatures. Climate–response analysis revealed that radial stem increment was promoted by the temperature in early summer, but also high precipitation in spring and in the year before tree-ring formation. Forest dynamics is also strongly influenced by anthropogenic activities. In addition to the natural forest dynamics, logging resulted in divergent growth trends within given age classes and habitats (forest interior and forest edge); overall, 22 groups of trees with different characteristics in the annual radial stem increment were identified. A tree-ring series-based reconstruction of logging intensity since 1935 suggests that moderate selective logging occurred throughout the study period. However, selective logging was strongly intensified after 1990 as the result of the breakdown of the Communist regime in Mongolia and the transition from centrally planned to market economy. Because tree stump densities showed that the ratio of felled to live trees was 2:1 in the interior or even 0.9:1 at the edges of the forests and most logging occurred during the past 20 years, it must be concluded that the forests of the Mongolian Altai are presently exploited far beyond the level of sustainability. A close correlation of the ratio of felled to live trees with the density of summer camps of pastoral nomads in the vicinity suggests that trees are primarily felled by the local population.     

The effect of missing rings on stand-age estimation of even-aged forests in northern Hokkaido,Japan

The effectiveness of estimating stand age from increment core samples taken at stump height (20 cm above ground) was tested in an even-aged stand ofBetula ermanii that had regenerated after a forest fire in 1945 in Hokkaido, Japan. Careful cross-dating revealed that annual rings were missing in 11 cores out of a total of 42 cores sampled, and that all these missing rings occurred in the outermost part of the core. These facts indicate that precaution has to be taken in selecting trees from which cores are to be sampled. The present work also revealed that those trees with missing rings have a characteristic appearance, with a thinner stem and less crown foliage than normal trees with complete rings. It was also found that even if this appearance test failed, the possibility of missing rings could be detected from a declining growth pattern, with extremely narrow rings on the increment core which normal trees did not show.     

Structural dynamics of a natural mixed deciduous forest in western Thailand

Abstract. Structural dynamics of a natural tropical seasonal – mixed deciduous – forest were studied over a 4-yr period at Mae Klong Watershed Research Station, Kanchanaburi Province, western Thailand, with particular reference to the role of forest fires and undergrowth bamboos. All trees > 5 cm DBH in a permanent plot of 200 m × 200 m were censused every two years from 1992 to 1996. The forest was characterized by a low stem density and basal area and relatively high species diversity. Both the bamboo undergrowth and frequent forest fires could be dominant factors that prevent continuous regeneration. Recruitment, mortality, gain (growth of survival tree plus ingrowth) and loss in basal area (by tree death) during the four years were 6.70%/yr, 2.91%/yr, 1.22%/yr and 1.34%/yr, respectively. Mortality was size dependent; middle size trees (30–50 cm) had the lowest mortality, while the smallest (5–10 cm) had the highest mortality. Tree recruitment was observed particularly in the first two years, mostly in the area where die-back of undergrowth bamboo occurred. The bias of the spatial distribution of recruitment to the area of bamboo die-back was significant and stronger than that to the forest canopy gaps. Successful regeneration of trees which survive competition with other herbs and trees after dieback of bamboo could occur when repeated forest fires did not occur in subsequent years. It is suggested that both the fire disturbance regime and bamboo life-cycle greatly influence the structure and dynamics of this seasonal tropical forest.     

黄岗山西北坡森林垂直带群落特征及区系分析

为研究森林垂直带的群落组成特征及其植物地理区系成分,于黄岗山西北坡从低海拔至高海拔设置5个群落带,依次为常绿阔叶林、常绿落叶阔叶混交林、针阔混交林、针叶林、中山苔藓矮曲林。通过统计分析,结果显示,黄岗山垂直带森林具有典型的中亚热带地带性植被特点,以常绿阔叶树和常绿针叶树为主要优势种;种的相似性指数表明,不同植被群落间物种组成具有较大的差异性,同时也说明黄岗山森林丰富的物种多样性;植物区系地理成分复杂多样,以热带成分为主,并具有由热带向温带过渡的性质。     

Radial growth response of major conifers to climate change on Haba Snow Mountain,Southwestern China

Climate change has an inevitable impact on forest ecosystems, to better understand the influence of climate change on forest growth, we analyzed the growth response of four major conifers to climate on Haba Snow Mountain in central Hengduan Mountains. Tree ring samples were taken from four species at their upper distributional limits, and residual chronologies were developed by using tree ring width data. Response function and redundancy analysis were taken to reveal the key climatic factors affecting tree growth and moving interval analysis was applied to detect the stability of growth-climate relationships. The results showed that previous November temperature, precipitation in current February, current May and current June were common factors affecting the radial growth of the studied species. Abies georgei was mainly influenced by the temperature in previous November. The photothermal condition in May and June controlled the growth of Larix potaninii. Moisture condition in previous August and current May was the key factor affecting Pinus densata growth. As for Pinus yunnanensis, the drought in current May was the limiting factor influencing its growth. The dynamic relationship between tree growth and climatic factors varied among species, and the results were consistent with response function analysis. A forecast in future forest growth on Haba Snow Mountain was complex, since future climate change had both positive and negative effects on the radial growth of four major conifers.     

哀牢山中山湿性常绿阔叶林木径向生长季节动态及其对气候因子的响应

研究采用树木生长环在哀牢山中山湿性常绿阔叶林持续9年(2009—2017年)监测了2个常绿树种(厚皮香,Ternstroemia gymnanthera;南亚枇杷,Eriobotrya bengalensis)和2个落叶树种(西桦,Betula alnoides;珍珠花,Lyonia ovalifolia)的树干月生长量,采用逻辑斯蒂生长模型(Logistic model)模拟树木径向生长量和物候参数,并分析了年、季尺度上径向生长与主要气候因子的关系。结果表明:1)4个树种年平均生长量为6.3 mm,落叶树种年平均生长量(10.6 mm/a)显著高于常绿树种(3.0 mm/a);2)雨季(5—10月)是哀牢山中山湿性常绿阔叶林树木生长的主要时期,4个树种雨季平均生长量为5.9 mm,占全年总生长量的93%,其中落叶树种雨季生长量占全年的96%,而常绿树种雨季生长量占全年的86%;3)常绿树种生长季长度为169天,长于落叶树种(137天),而落叶树种最大生长速率(0.14 mm/d)显著高于常绿树种(0.03 mm/d),最大径向生长速率能很好地预测树种年生长量;4)低温、雾日和光合有效...     

太白山红桦种群结构与空间分析

 为了揭示太白山红桦(Betula albo-sinensis)种群的维持机制, 结合径级结构、静态生命表和存活曲线, 对太白山红桦种群结构进行了研究; 并应用单变量、双变量K函数对不同径级立木与残干的空间格局、空间关联性进行了多尺度分析。研究显示, 太白山红桦种群在幼苗幼树阶段死亡率较高, 进入中龄期后死亡率有所降低, 随着年龄增长, 死亡率逐渐增加, 直至年龄极限。其存活曲线基本接近Deevey I型(曲线凸型)。其个体死亡方式主要为掘根和折干(由大雪所致), 能够为种群更新提供潜在空间。除海拔2 250 m立木整体格局呈集群分布外, 该地区红桦立木与残干在不同尺度下的整体格局均为随机分布。不同发育阶段的个体均呈集群分布, 表现为斑块状同龄群。在红桦更新所需的最适林窗大小尺度上, 红桦立木与残干的空间关联性为显著正相关。以上结果表明: 太白山红桦种群具有同龄集群生长的特性, 种群由时空上不连续的局部斑块同龄个体组成, 其更新有赖于以掘根及折干方式死亡个体所形成的林窗斑块, 这种以局部林窗斑块更新维持种群整体稳定的特性, 可能是其长期稳定存在的重要机制。     

科尔沁沙地不同密度(小面积)樟子松人工林生长状况

在内蒙古科尔沁沙地丘间片林中选择不同密度的樟子松样地,对樟子松在不同栽植密度条件下的生长情况进行了研究.由于受多年降水偏少的影响,科尔沁沙地的樟子松出现了大量枯梢继而死亡的现象,而这种现象与林地的密度存在很强的相关性.样地林木的死亡率随林地密度的加大呈幂函数关系增加,原先最高密度情况下的林地,保存到现在的活木数量反而最少;林木的平均死亡年龄、最早死亡年龄、冠幅、树高和胸径随林地密度的增加而减小.虽然在其它一些区域的研究结果表明,树高较少受竞争的影响,但是在半干旱区,树高仍然与密度相关.枯梢林木的比例在高密度的样地大于低密度的样地,枯梢对低密度样地的林木基本上没有大的影响.各样地的冠幅和胸径比相差不大,平均只有0.297,以此指标衡量,该地可能更适合单一樟子松林的种植.综合来看,科尔沁沙地的气候和土壤条件适合栽植樟子松,但初始密度应控制在2800株/hm2以下,并应根据生长情况在进入生长高峰期后对林木进行适时间伐,20a龄期的林木其密度保持在2100株/hm2左右比较适宜.