城市与山地森林地区夏秋季大气CO2浓度变化初探

城市与山地森林地区夏秋季大气ＣＯ２浓度变化初探蒋高明黄银晓韩兴国（中国科学院植物研究所，北京１０００９３）关键词ＣＯ２浓度；城市；森林；北京市．１引言ＣＯ２等温室气体的增加，引起了全球科学家与政治家的关注，温室效应及其带来的一系列生态环境改变即全球...     

千烟洲试区人工林营养元素生物积累的研究

对千烟洲试验区人工林的植物和土壤中１５种营养元素的含量、分布和生物积累特征进行了研究。结果表明,两块人工林土壤中缺乏Ｎ、Ｐ、Ｃａ３种元素,微量营养元素未发现亏缺现象。草本层的养分含量高于乔木层的养分含量。两块人工林的生物吸收系数均以Ｐ、Ｃａ、Ｎ的吸收系数最大,Ｔｉ元素的生物吸收系数最低,其余的养分元素均属弱积累中等摄取的营养元素     

保靖县油桐林分混交模式及其生态经济效益

湖南省保靖县是我国主要的油桐产区之一。针对该县多年来由于油桐林分结构单一而产生的诸多生态和经济问题，提出了桐树混交、桐灌混交和桐草混交三种改造模式，并对其生态和经济效益进行了分析。     

Fluctuations of Climatic Conditions, Elemental Cycling and Forest Growth at the Watershed Scale

The relationships between fluctuations in climatic conditions,forest productivity and elemental cycling were studied from 1994 to 1997 in a headwater catchment of the southern Laurentians dominated by sugar maple (Acer saccharumMarsh.) growing on podzolic soils. Annual budgets show that H⁺, K, and NO₃ were retained in the watershed whileCa, Mg and Na were lost. The magnitude of the net annual budget for Ca, Mg and Na was correlated to annual variationsin precipitation with the absolute budget value decreasing during dry years. Stemwood (r² = 0.85) and total tree biomass production (r² = 0.99) were correlated with mean annual temperature but fine roots and leaf litter werenot. During the growing season, the pH of the organic horizons(FH) decreased as the volumetric water content of soildecreased. A positive association was also found between airtemperature and H₂O-soluble (r² = 0.88) and PO₄-extractable (r² = 0.99) SO₄ in the upper B horizon. On a multi-year scale, we suspect that the decreasein the storage of inorganic SO₄ in the soil results from the cumulative effects of annual variations in climatic conditions superimposed on the long-term decrease in SO₄deposition from the atmosphere. These soil changes were reflected by a decline in SO₄, Ca and Mg concentrationsin the stream. The generalisation of the observed short-term patterns to longer time scales must be approached with caution. Yet, our results indicate that the associations between climatic variations and the biogeochemistry of the ecosystem occur at different spatial and temporal scales and integrate abroad range of chemical components and ecosystem compartments. This reflects the inherent complexity of natural systems and offers a vast palette of indicators of the response of terrestrial ecosystems to variations in the intensity of environmental factors such as climatic conditions.     

An Analysis of the Daily Radial Activity of 7 Boreal Tree Species, Northwestern Quebec

In the `Des Vieux Arbres' ecological reserve situated within northwestern Québec, 40 band dendrometers were installedon 7 of the major boreal tree species. The late Spring–early Summer daily radial activity registered in 1997 was related todaily weather variables. For each tree species, the daily mean i) cumulative radial increment and ii) radial activity indexedseries obtained by first-difference standardization were analyzed. The results indicate the existence of strong similarities among the 7 species. All showed strong synchronousfluctuations in radius during late winter and early spring. Thisperiod ended with a short but sharp increase in radial increments that marked the passage of water into the stem. Thisinitial swelling, less obvious in Pinus species was followed by a prolonged period of little change in radial activity. Meteorological data indicated that air temperature waspositively related to stem swelling during the late winter–earlyspring period. Both air and soil temperatures became negatively related to radial expansion once the passage of water has occurred in the stem. Starting in early June, all species registered a sustained increase in radial increments possiblyassociated with active cell division. After this, radial expansion was negatively related to air temperature and positively to rainfall.     

Ice Storm Damage and Early Recovery in an Old-Growth Forest

We quantified the damage causedby a major ice storm to individual trees in two1-ha permanent plots located at Mont St. Hilairein southwestern Québec, Canada. The storm, whichoccurred in January 1998, is the worst on recordin eastern North America; glaze ice on the orderof 80–100 mm accumulated at our study site. Allbut 3% of the trees (DBH 10 cm) lost at leastsome crown branches, and 35% lost more than halftheir crown. Damage to trees increased in the order: Tsuga canadensis, Betula alleghaniensis, Ostrya virginiana, Acer saccharum, Fagus grandifolia, Quercus rubra, Betula papyrifera, Acer rubrum, Tilia americana, and Fraxinus americana. Only 22% of the saplings and small trees (4 cm < DBH < 10 cm)escaped being broken or pinned to the ground byfalling material. Levels of damage generally weregreater in an exposed ridge top forest than in acove protected from wind. By August 1999 only53% of the trees had new shoots developing fromthe trunk or broken branches; among the moredominant canopy trees, Fagus grandifoliahad the least sprouting and Acer saccharumand Quercus rubra the most. We anticipateand will monitor both significant turnover in thetree community and some shift in composition ofthe canopy dominants.     

Precision And Accuracy Of Pest And Pathogen Damage Assessment In Young Eucalypt Plantations

Fungal pathogens, browsing mammals, birds, insects, nutrient deficiencies, drought, frost and waterlogging are all damaging agents to plantation species. The subsequent loss in leaf tissue or reduced photosynthetic potential can reduce growth and potentially lead to tree death. The Crown Damage Index (CDI) was developed in Australia to quantify damage in young eucalypt plantations. The accuracy and precision of assessing damage at a tree level were determined to ensure the reliability, objectivity and repeatability of the CDI method. Nine assessors, with varying levels of experience, estimated damage on three plots of fifty trees each, to obtain an understanding of the subjectivity of assessing damage caused by insects (e.g. Chrysophtharta spp.) and fungal pathogens (e.g. Mycosphaerella spp.) on Eucalyptus globulus. Damage levels were measured by destructive sampling to enable direct comparisons between estimates and damage levels to be made. The most experienced assessors provided the most repeatable estimates and were generally the most accurate. The incidence of foliar necrosis was the least subjective measure while defoliation was the most subjective and the least accurate of the indices measured. All assessors, regardless of experience, were able to predict the Crown Damage Index (a combined index of all damage classes) to within 12% of measured damage levels.     

RELATIONSHIP BETWEEN BASAL SOIL RESPIRATION RATE, TREE STAND AND SOIL CHARACTERISTICS IN BOREAL FORESTS

Soil respiration is considered to represent the overall microbial activity reflecting mineralisation of organic matter in soil. It is the most commonly used biological variable in soil studies. In long-term monitoring of forested areas, there is a need for reference values for soil microbiological variables in different forest ecosystems. In this study we describe the relationship between soil respiration rate, tree stand and humus chemical characteristics of boreal coniferous forests stands. Soil respiration rate was higher in pine dominated than in spruce dominated study sites when the result was calculated on dry matter bases. However, when calculated on area bases, the result was opposite and no difference was found when the soil respiration rate was calculated on organic carbon bases. Irrespective of the main tree species, the soil respiration rate was equal in different development classes but not equal in soil fertility classes, i.e. within forest site types based on differences in ground vegetation. Respiration rates were clearly higher in mesic sites when calculated on dry matter, C_org or area bases. However, soil respiration rate did not correlate with soil chemical variables indicating site fertility. Soil respiration rate on dry matter basis was at a lower level in the south and on more fertile sites, and on the other hand at a higher level in older stands and on sites with a thicker organic layer.     

A comparison of fixed-site and non-fixed-site approaches for species protection

The efficacy of simultaneously advancing two distinct conceptual designs (referred to here as fixed-site and non-fixed-site) for species conservation and protection is addressed. In the literature, numerous models can be found that typically stem from a particular design, but rarely are comparisons made between approaches. This paper presents a more integrated optimization framework that models landowner behavior and species viabilities at a landscape scale. Regional demand for resource extraction is used as the economic driver, a variant of simulated annealing is used to solve the model under different species protection approaches, and a detailed species population simulator is utilized to measure biological responses. When directly comparing the outcomes of different species protection strategies from a case study in Oregon (USA), it was found that neither approach was universally superior in terms of financial value or degree of protection for two late seral forest dependent species.