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1.
Climatic signal of earlywood vessels of oak on a maritime site   总被引:1,自引:0,他引:1  
Earlywood vessel lumen areas were measured in 72 consecutive tree rings in wood cores from oak (Quercus robur L.) trees in a maritime woodland. This anatomical time series was statistically correlated with climate data for the same time span. There was a strong dependence of earlywood vessel lumen area on rainfall between February and April, which reflects the role of water availability in vessel ontogeny. By inversion, earlywood vessel lumen areas can be used as a proxy to reconstruct spring precipitation beyond the archived weather records. Such information may be of value in the context of climate change.  相似文献   

2.
3.
Measured values of four key leaf traits (leaf area per unit mass, nitrogen concentration, photosynthetic capacity, leaf lifespan) co-vary consistently within and among diverse biomes, suggesting convergent evolution across species. The same leaf traits co-vary consistently with the environmental conditions (light intensity, carbon-dioxide concentration, nitrogen supply) prevailing during leaf development. No existing theory satisfactorily explains all of these trends. Here, using a simple model of the carbon-nitrogen economy of trees, we show that global leaf-trait relationships and leaf responses to environmental conditions can be explained by the optimization hypothesis (MAXX) that plants maximize the total amount of carbon exported from their canopies over the lifespan of leaves. Incorporating MAXX into larger-scale vegetation models may improve their consistency with global leaf-trait relationships, and enhance their ability to predict how global terrestrial productivity and carbon sequestration respond to environmental change.  相似文献   

4.
Possibilities to improve the expressed population signal (EPS) derived from tree-ring chronology were studied on 19 trees sampled from a permanent Scots pine (Pinus sylvestris L.) thinning experiment in southern Finland. Trees of varying relative size from thinned and unthinned control plots, as well as radii in different compass directions and different positions along the stem, were compared. The EPS values increased with increasing number of chronologies sampled. The effect of increasing tree number was more pronounced compared to increasing number of radii per tree. EPS also increased when the social status of a tree improved, but no clear differences were found between unthinned and thinned plots. Furthermore, no clear trend existed between different heights along the stem. The highest EPS values occurred in the directions west, southwest, and south; correspondingly, the lowest value was on the north side of the bole, followed by the northeast and east. It was concluded that some reduction in the noise present in tree-ring chronologies can be achieved by paying more attention to sample selection within and between stems. The sunny side of the bole especially, as well as dominant trees, should be preferred. However, the most important factor in noise reduction is adequate replication.  相似文献   

5.
We present a new model of tree growth, DESPOT (Deducing Emergent Structure and Physiology Of Trees), in which carbon (C) allocation is adjusted in each time step to maximize whole-tree net C gain in the next time step. Carbon gain, respiration and the acquisition and transport of substitutable photosynthetic resources (nitrogen, water and light) are modeled on a process basis. The current form of DESPOT simulates a uniform, monospecific, self-thinning stand. This paper describes DESPOT and its general behavior in comparison to published data, and presents an evaluation of the sensitivity of its qualitative predictions by Monte Carlo parameter sensitivity analysis. DESPOT predicts determinate height growth and steady stand-level net primary productivity (NPP), but slow declines in aboveground NPP and leaf area index. Monte Carlo analysis, wherein the model was run repeatedly with randomly different parameter sets, revealed that many parameter sets do not lead to sustainable NPP. Of those that do lead to sustainable growth, the ratios at maturity of net to gross primary productivity and of leaf area to sapwood area are highly conserved.  相似文献   

6.
Industrial applications of natural gums have been expanding tremendously, so gum collection from trees provides an important livelihood for local dwellers in drought-prone Rajasthan and its surroundings states. Traditional gum tapping is crude and unscientific; deep incision, untimely extraction and high concentration of chemicals in gum have affected Sterculia urens species in its natural habitat. In studies 2 years on trees having diameter at breast height [40 cm from natural stands to maximize gum collection and standardize the tapping method(bore holes vs. V blazes), tapping season, chemical and concentration, different tapping techniques were tested. For tapping maximum gum was collected using bore hole. Ethephon was better as extraction chemical than sulphuric acid. Bore-hole tapping with a 5-cm hole and ethephon at 300 mg/m L yielded the most gum(135.20 g/tree). Ethephon at 300 mg/m L yielded the most gum.Ethephon induced gummosis without affecting the health of tree. Tapping seasons also significantly affected the gum yield; the most gum was obtained in April–June.  相似文献   

7.
The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g·m−2·month−1 in June 2004 (simplified expression of g (carbon)·m−2·month−1) and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g·m−2·a−1 (simplified expression of g (carbon)·m−2·a−1) during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit (VPD) and temperature. Under humid conditions (VPD < 1.0 kPa), the gross ecosystem production (GEP) increased with increasing temperature. But the net ecosystem production (NEP) showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment (VPD > 1.0 kPa), the GEP decreased with the increasing VPD at a rate of 3.0 μmol·m−2·s−1·kPa-1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol·m−2·s−1·kPa−1. Under humid conditions (VPD < 1.0 kPa), both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.  相似文献   

8.
The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 (simplified expression of g (carbon).m^-2.month^-1) and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 (simplified expression of g (carbon).m^-2.a^-1) during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit (VPD) and temperature. Under humid conditions (VPD 〈 1.0 kPa), the gross ecosystem production (GEP) increased with increasing temperature. But the net ecosystem production (NEP) showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment (VPD 〉 1.0 kPa), the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions (VPD 〈 1.0 kPa), both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.  相似文献   

9.
龟甲竹光合生理特性及其与主要影响因子关系   总被引:1,自引:0,他引:1  
运用Li-6400便携式光合分析仪,以2年生龟甲竹为研究对象,测定光合日变化、光响应曲线,并拟合得出多个光合生理指标.结果表明,龟甲竹净光合速率日变化呈单峰曲线,峰值出现在9:00左右,约4.25μmol/(m2·s);最大净光合速率为9.18μmol/(m2·s),光补偿点为14.93 μmol/(m2·s),光饱和点为812.58 μmol/(m2·s),表观量子效率为0.053,表现出较强的弱光利用能力.通径系数分析表明,影响龟甲竹净光合速率日变化的主要生理生态因子为大气湿度>叶温>气孔导度>光照有效辐射.  相似文献   

10.
白桦和新疆杨树干茎流变化规律及与环境因子的关系   总被引:1,自引:0,他引:1  
对白桦和新疆杨在7~10月的树干茎流速率变化规律及其与环境因子的关系进行了研究,结果表明:白桦的茎流日变化过程呈现单峰曲线,且变幅大,而新疆杨则呈现多峰曲线;茎流速率与环境温度呈显著正相关,与环境湿度呈显著负相关,与大气气压无显著相关性。两树种树干茎流到达峰值的时刻均表现为秋季比夏季晚约1 h,且新疆杨比白桦到达峰值的...  相似文献   

11.
针对立交桥附属绿地的特殊环境,选取了24个植物品种(地被植物16种、藤本植物6种、灌木2种)采取人工遮荫处理的方法,测定这些植物品种的耐荫性,根据各项生理指标的检测结果,筛选出耐荫性好、适合济南市立交桥下栽植的植物有:大叶铁线莲、玉簪、紫玉簪等16种。  相似文献   

12.
塑料废弃物形成的白色污染已成为新世纪困扰人类生存环境与人类自身发展的问题之一。而在白色污染中,农用地膜、一次性废弃餐具及包装用一次性塑料袋、塑料膜是最为棘手的,而且占有相当的比例。相关专家认为治理白色污染的对策就是以发展和回收再利用技术为主,辅之以社会行为和其他技术。新型  相似文献   

13.
Our comparative analysis of forest research networks indicates the emergence and strengthening of a new model of knowledge co-production involving knowledge producers and users, with the goal of fostering innovation and addressing challenges facing the forest sector. However, effective movement towards this model requires attention to design and to management, particularly in relation to the expectations of partners (both university and non-university) who are used to traditional models of knowledge production and linear processes of knowledge extension. Based on our survey and literature review, we argue that in the short-term, the objective of producing applied research requires that forest research networks prioritize diverse and tailored knowledge mobilization strategies, rather than emphasizing knowledge production. With regards to the longer-term objective of facilitating new avenues for innovation in the forest sector this requires a knowledge mobilization strategy that entails a level of engagement with partners that is creative and transformative rather than mainly informative. Building an organizational culture of innovation requires a different approach to producing applied research, although many of the same skills are required. Our analysis suggest that if networks are to be effective in both these short and long term objectives, they should foster openness by establishing transparent and responsive organizational processes. Although such policies may exist and be available to partners, we found relatively little information available on the processes of transparency, accountability and conflict resolution within the websites of the networks we compared. Establishing clear roles and consistent channels of communications is imperative to facilitate the efficient and effective management of the network and manage partners' expectations, regardless of the partnership model.  相似文献   

14.
Calliandra calothyrsus was cut back at monthly intervals during the rainy season between January and May to determine which period of cutting gives the highest quantity and quality of dry matter in August, the peak of the dry season, when a lack of fodder is most acute. In both 1992 and 1993, the highest quantity of dry season production was obtained from the plots that were harvested in February, six months before the driest month. Crude protein content of the dry season fodder was not significantly influenced by the time of harvest in the rainy season. How the fodder produced in the dry season is to be used to satisfy the digestible protein needs of 3.5 goats for a 90-day period in the highlands of Burundi and how the leafy biomass harvested in the rainy season is to be used to support crop production are discussed.Deceased  相似文献   

15.
There is growing interest in using ecosystem services to aid development of management strategies that target sustainability and enhance ecosystem support to humans. Challenges remain in the search for methods and indicators that can quantify ecosystem services using metrics that are meaningful in light of their high priorities. We developed a framework to link ecosystems to human wellbeing based on a stepwise approach. We evaluated prospective models in terms of their capacity to quantify national ecosystem services of forests. The most applicable models were subsequently used to quantify ecosystem services. The Korea Forest Research Institute model satisfied all criteria in its first practical use. A total of 12 key ecosystem services were identified. For our case study, we quantified four ecosystem functions, viz. water storage capacity in forest soil for water storage service, reduced suspended sediment for water purification service, reduced soil erosion for landslide prevention service, and reduced sediment yield for sediment regulation service. Water storage capacity in forest soil was estimated at 2142 t/ha, and reduced suspended sediment was estimated at 608 kg/ha. Reduced soil erosion was estimated at 77 m3/ha, and reduced sediment yield was estimated at 285 m3/ha. These results were similar to those reported by previous studies. Mapped results revealed hotspots of ecosystem services around protected areas that were particularly rich in biodiversity. In addition, the proposed framework illustrated that quantification of ecosystem services could be supported by the spatial flow of ecosystem services. However, our approach did not address challenges faced when quantifying connections between ecosystem indicators and actual benefits of services described.  相似文献   

16.
本文从环境保护的观点,论述了公路绿化的重要性。通过惠河高速公路的绿化设计和施工,进一步阐述公路绿化工程是公路设计和施工的重要组成部分,亦是绝对不可缺少的设计内容,它关系到水土保持,保护自然和绿化家园的重要问题。  相似文献   

17.
(超)轻型飞机防治森林病虫害选型的研究   总被引:4,自引:1,他引:4  
通过对 3种 (超 )轻型飞机的主要技术性能比较、作业技术指标对比和其使用、作业情况和实用性、适用性研究 ,结果表明蜜蜂 3、A - 1B超轻型和海燕 6 5 0B轻型飞机都适合闽北林区的防治作业 ,但海燕 6 5 0B具有更多的优越性 ,适应性更强 ,实用性更高 ,是 3种机型中防治作业较理想的一种轻型飞机  相似文献   

18.
This study focuses on age,growth rate and diameter distribution of pine forests in the Malam Jabba area,Swat District,Pakistan.Wood core samples were taken from twenty stands.Picea smithiana was the oldest at 234 years with a 112-cm diameter.Abies pindrow was 125 years with an 80-cm diameter while the oldest Pinus wallichiana was 122 years with 75-cm diameter.The fastest overall growth rate of 1.5±0.1 year/cm was for P.wallichiana on a west-facing aspect,while the slowest 5.8±2.6 year/cm growth was P.smithiana on an eastfacing exposure.P.wallichiana and A.pindrow exhibited marked differences in growth rates over a 5-year period.The highest growth was by P.wallichiana from 1966 to 2006.A.pindrow showed less growth over the same years,such pattern simultaneously reverse from 1911 to 1965.The relationship between diameter and age,diameter and growth rate and age and growth rate were correlated.P.wallichiana and A.pindrow ages were correlated with diameter and growth rates.P.smithiana age was positive correlated with diameter.Generally,topographic and edaphic factors did not show significant correlations with growth rates,although some appreciable correlations were recorded.The growth of P.wallichiana was correlated with elevation while A.pindrow was correlated with maximum water retaining capacity.Diameter and age produced uneven size classes and many size gaps,which could be the result of anthropogenic disturbances.  相似文献   

19.
The relationships between climate conditions and wood density in tropical forests are still poorly understood.To quantify spatial dependence of wood density in the state of Minas Gerais(MG,Brazil),map spatial distribution of density,and correlate density with climate variables,we extracted data from the Forest Inventory of Minas Gerais for 1988 trees scaled throughout the territory and measured wood density of discs removed from the trees.Environmental variables were extracted from the database ...  相似文献   

20.
Long-term investigations of Scots pine (Pinus sylvestris L.) growth were carried out in the vicinity of one of the biggest air pollution sources in Lithuania—mineral fertilizers plant “Achema.” It is detected that initial stages of the dynamic tree response to the external stress factors in the polluted environment with an increased quantity of nitrogen compounds have started with a stimulation stage, followed by a gradual transition to a depression of growth. The recovery of the damaged stands took place along with the reduced environmental pollution, and the overdraft of the “normal” annual increment was a characteristic feature of all the investigated stands. This phase is still continuing for the most damaged stands. A very high individual variability of the tree growth response to the environmental impact is a characteristic feature of the damaged Scots pine stands. The homeostatic mechanisms of the survived trees stipulated reaching approximately the same or even higher growth rate as prior to the depression period, and the tree growth rate before the depression period can serve as the most powerful predictor of tree growth recovery capacity under the reduced environmental pollution. Crown defoliation is the next most important predictor of individual tree recovery capacity. Lower stand density and lower competition cause higher recovery capacity of damaged trees. The conclusion is made that a reduction in the environmental pollution on the local and regional scale and especially a decrease in emissions and deposition of sulfur and nitrogen compounds caused the recovery of damaged forests. These trends should be taken into account while analyzing and modeling forest dynamics. Interaction of environmental pollution and climatic factors is very important for the response of tree growth to the environmental stressors.  相似文献   

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