Stricter Ozone Ambient Air Quality Standard Has Beneficial Effect on Ponderosa Pine in California

Ambient air quality standards and control strategies are implemented to protect humans and vegetation from adverse effects. We used a process-based tree-growth model (TREGRO) to show that over the past 37 years, changes in O₃ exposure, with accompanying variation in climate, are reflected in changes in the growth of Pinus ponderosa Dougl. ex Laws. in the San Bernardino Mountains near Los Angeles, California, USA. Despite variation in temperature and precipitation over the study period (1963–1999), O₃ exposure consistently reduced simulated tree growth. Simulated growth reductions increased concurrent with increasing O₃ exposure. The maximum growth reduction occurred in 1979. As O₃ exposures decreased during the 1980s and 1990s, effects on growth also decreased. This implies that emission control strategies taken to reduce exposures to attain O₃ standards benefited P. ponderosa growth in the San Bernardino Mountains. This modeling approach provides a powerful tool for solving the difficult problem of evaluating regulatory effectiveness by simulating plant response using long-term climate and air pollution exposure records for a given region.Phone 541 754-4621 Fax 541 754-4799     

Contribution of ambient ozone to Scots pine defoliation and reduced growth in the Central European forests: a Lithuanian case study

The study aimed to explore if changes in crown defoliation and stem growth of Scots pines (Pinus sylvestris L.) could be related to changes in ambient ozone (O₃) concentration in central Europe. To meet this objective the study was performed in 3 Lithuanian national parks, close to the ICP integrated monitoring stations from which data on meteorology and pollution were provided. Contribution of peak O₃ concentrations to the integrated impact of acidifying compounds and meteorological parameters on pine stem growth was found to be more significant than its contribution to the integrated impact of acidifying compounds and meteorological parameters on pine defoliation. Findings of the study provide statistical evidence that peak concentrations of ambient O₃ can have a negative impact on pine tree crown defoliation and stem growth reduction under field conditions in central and northeastern Europe where the AOT40 values for forests are commonly below their phytotoxic levels.     

不同植茶年限土壤氮素组分变化及其与环境因子关系

茶园土壤氮素组分变化影响茶园土壤供氮能力和氮素循环.以植茶30、50和70 a的茶园土壤为研究对象,探讨不同植茶年限土壤氮素组分变化特征及其与理化性质和酶活性之间的关系.结果表明：①随着植茶年限的增加,粉粒、全磷、脲酶和过氧化氢酶活性逐渐增加,砂粒、黏粒、pH、电导率、有机碳和蔗糖酶活性逐渐降低,碱性磷酸酶活性先增加后降低,土壤含水量和酸性磷酸酶活性无显著变化.②随着植茶年限的增加,酸解性铵态氮、氨基酸态氮和硝态氮含量显著增加,且茶园土壤全氮、酸解性铵态氮、未知态氮和非酸解氮含量显著高于林地.③全磷、碱性磷酸酶和脲酶是土壤氮素组分变化的主要影响因子.其中,有机氮组分与全磷、碱性磷酸酶活性具有显著相关性,无机氮组分与碱性磷酸酶活性具有显著相关性,全氮与砂粒、粉粒、全磷、脲酶和碱性磷酸酶活性具有极显著的相关性.     

Remote Assessment of Forest Health in Southern Arizona, USA: Evidence for Ozone-Induced Foliar Injury

This paper examines possible ozone-induced foliar injury to ponderosa pine areas in the Rincon Mountains of southern Arizona from 1972 to 1992. Spatiotemporal differences in a satellite-derived vegetation index (VI) are examined with respect to antecedent moisture conditions, temporal variations in ozone exposure levels, and measured foliar injury values from 1985. Seasonal ozone exposure levels (SUM60 and W126) increased from 1982 to 1998 and were significantly correlated (r = 0.49 and 0.53, α= 0.05) with annual population totals in the Tucson area. Extensive masking of satellite images from 1972, 1986, and 1992 resulted in two optimal change detection areas, with one site, TVWMica, exposed mostly to the Tucson air pollution plume, while the other site, EMica, was more protected from Tucson-derived pollution. An overall increase in VI from 1972 to 1992 at both sites appears to have been caused by an increase in moisture availability. Larger foliar injury values in 1985 were associated with a smaller increase in VI (i.e., a smaller increase in green leaf biomass) from 1972 to 1986. From 1972 to 1986 and from 1986 to 1992, VI values at TV/WMica increased at a slower rate compared to those at EMica. The reduced increase in “green-up” may have been caused partially by ozone-induced foliar injury and resulting decreases in green leaf biomass. However, these spatial differences in VI values may have also been caused by a number of other factors. Results nevertheless reveal the strong possibility of distinct, topographically based, spatial variations in ozone-induced foliar injury within the Rincons.     

如何在红松母树林内实施计划烧除

林口林业局通过对红松母树林下的细小可燃物进行计划烧除实验,证明这种方法不但是预防森林火灾、保护红松母树林安全的有效措施,而且还可消除森林病害虫和增加林木生长量。     

Ecological Variation in the Morphological Structure of the Crown in Siberian Stone Pine at the Timberline

The structure of the crown and branching; the growth, development, and ontogeny of branches; and organogenesis and growth of female shoots in the model Siberian stone pine trees were studied in four types of habitats at the timberline in the central Altai Mountains (1700–2170 m a.s.l.). The results provided evidence that the ecological forms of trees appear due to changes in the pattern of branching as well as to the decreased rate of vegetative (primarily apical) growth. The diameter of the shoot pith is one of the most variable characters reflecting the deterioration of environmental conditions at higher elevations.     

不同母岩区马尾松人工林土壤酶活性及微生物学性质研究

红壤丘陵区马尾松人工林对土壤性质有重要影响。研究马尾松长期种植对该区主要母岩（花岗岩、第四纪红黏土和红砂岩）发育土壤酶活性及微生物学性质的影响。微生物性质结果显示,土壤微生物生物量碳氮在花岗岩区较高,但有机碳在第四纪红黏土区矿化相对强烈;0～20 cm土层,花岗岩区和红砂岩区土壤有机碳相对趋向累积,而20～40 cm土层,第四纪红黏土区土壤有机碳相对累积;花岗岩区林地土壤微生物群落相对稳定,且0～20 cm层土壤微生物群落真菌较多。转化酶活性和脲酶活性在花岗岩和第四纪红黏土区较高;酸性磷酸酶活性在第四纪红黏土区显著较高;各母岩区土壤多酚氧化酶活性无显著性差异;过氧化氢酶活性在花岗岩区显著较高;因此,在马尾松与土壤长期作用下,花岗岩区土壤微生物群落稳定性,生化强度较高,相对适宜马尾松林种植。     

Poplar plantation has the potential to alter the water balance in semiarid Inner Mongolia

Poplar plantation is the most dominant broadleaf forest type in northern China. Since the mid-1990s plantation was intensified to combat desertification along China's northwestern border, i.e., within Inner Mongolia (IM). This evoked much concern regarding the ecological and environmental effects on areas that naturally grow grass or shrub vegetation. To highlight potential consequences of large-scale poplar plantations on the water budget within semiarid IM, we compared the growing season water balance (evapotranspiration (ET) and precipitation (PPT)) of a 3-yr old poplar plantation (Kp₃) and a natural shrubland (Ks) in the Kubuqi Desert in western IM, and a 6-yr old poplar plantation (Bp₆) growing under sub-humid climate near Beijing. The results showed that, despite 33% lower PPT at Kp₃, ET was 2% higher at Kp₃ (228 mm) as compared with Ks (223 mm) in May–September 2006. The difference derived mainly from higher ET at the plantation during drier periods of the growing season, which also indicated that the poplars must have partly transpired groundwater. Estimated growing season ET at Bp₆ was about 550 mm and more than 100% higher than at Kp₃. It is estimated that increases in leaf area index and net radiation at Kp₃ provide future potential for the poplars in Kubuqi to exceed the present ET and ET of the natural shrubland by 100–200%. These increases in ET are only possible through the permanent use of groundwater either directly by the trees or through increased irrigation. This may significantly change the water balance in the area (e.g., high ET at the cost of a reduction in the water table), which renders large-scale plantations a questionable tool in sustainable arid-land management.     

Can intensive management increase carbon storage in forests?

A possible response to increasing atmospheric CO₂ concentration is to attempt to increase the amount of carbon stored in terrestrial vegetation. One approach to increasing the size of the terrestrial carbon sink is to increase the growth of forests by utilizing intensive forest management practices. This article uses data from the literature and from forest growth and yield models to analyze the impact of three management practices on carbon storage: thinning, fertilization, and control of competing vegetation. Using Douglas-fir (Pseudotsuga menziesii) and loblolly pine (Pinus taeda) as example species, results from experiments with computer simulation models suggest that, for these two species, thinning generally does not increase carbon storage and may actually cause a decrease. The exception is thinning of very dense young stands. Fertilization generally increases carbon storage, although the response can be quite variable. The largest gains in carbon storage are likely to come from fertilizing lower-quality sites and from fertilizing thinned or less dense stands. Forests usually show increased growth in response to fertilization over a wide range of ages. Simulation of the growth of loblolly pine indicates that controlling competing vegetation at an early age helps to maximize stand growth and carbon storage. The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract number 68-C8-0006 to NSI Technology Inc. It has been subjected to the agency’s peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.