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1.
An understanding of forest carbon budgets, such as the factors that influence different levels of carbon accumulation, is one of the first steps in protecting and restoring areas of plant cover. Univariate and multivariate regression analysis was applied to evaluate the influence of climate variables (Rainfall, and mean maximum and minimum temperatures) on intra-annual above-ground carbon accumulated in tree species of the Caatinga. Above-ground carbon accumulated in the trees was 0.06 Mg ha?1 month?1. Carbon allocation in the aerial parts of the trees increased significantly with rainfall. Maximum and minimum temperature had little influence on carbon storage; however, variations in carbon accumulation are best explained when minimum and maximum temperatures are added to the regression model for rainfall, thereby demonstrating the simultaneous effect of these variables, and better explaining the carbon increase.  相似文献   

2.
This article addresses the German debate on the issue of the common welfare designation of public forests. In the first part, drawing on two case studies, the political discourse on the issue is introduced. Two major competing ‘story lines’ can be made out that are both based on a long tradition of controversially discussed concepts of regulatory forest policy. While they both emphasise that common welfare services in forestry run counter to profit orientation, they fundamentally differ with regard to the consequences for forest policy, e.g., considering the degree of state intervention. Afterwards, an overview on the scientific debate on common welfare in the German context is given, and different concepts of common welfare determination are distinguished. Existing approaches of common welfare determination in German forest policy are related to these concepts and discussed. It is argued that the common welfare designation of the public forest is only insufficiently implemented by the actual governance arrangements. Based on this consideration, eventually, the implementation of a procedural concept of common welfare operationalisation in Germany’s public forests at the local level is proposed. While such a concept will not solve all complex problems related to the determination of common welfare in public forestry, it would notably contribute to a more operational definition of common welfare in public forestry and a more informed public debate on the issue.  相似文献   

3.
Models constructed from machine learning are a potential non-parametric alternative for the prediction of biometric variables in opposition to traditional regression modeling. The hypothesis of this study was that the non-parametric approach with the k-Nearest-Neighbor algorithm (k-NN) has the possibility of presenting better accuracy with lower demand for predictor variables in the estimates of T. grandis trunk volume than the traditional volumetric models applied in forest sciences. Ten volumetric models were adjusted. In the regression k-NN was defined as maximum of 25 (25-NN), but with learning only for the odd neighbors starting at 3-NN. The optimal k nearest neighbor for two variations of predictors was obtained through repeated cross-validations. Spurr (ln) and Schumacher-Hall were the most accurate linear models that meet the linear regression assumptions. The optimal k nearest neighbor for the algorithm was k = 5 for the two variations of predictors. The use of the k-NN estimator may be a more general approach to linear regression especially when the assumptions made about the errors are not satisfied. However, its use should be considered only when traditional linear regression models or other simpler methods do not show good results.  相似文献   

4.
Vertical gradients incorporate multiple resources gradients which vary continuously. Therefore, research on mountain flo-ristic patterns along vertical gradients is important to reveal regular patterns of the flora along environmental gradients and to under-stand the changes in biodiversity along these gradients and their biological fitness. This study was designed to explore the character-istics of the floral compositions and ecological significance of floristic patterns along the vertical gradients of the National Nature Reserve of Dawei Mountain, located in the southeast of Yunnan Province. We analyzed the structural characteristics of the flora and the distribution patterns of its floristic components as a function of elevation on the basis of our field investigations along vertical vegetation transects. We carried out a systematic cluster analysis in order to determine the dividing line of floristic changes by eleva-tion along gradients and studied the effects of mountain climate on the vertical variation of floristic composition. The study shows: 1) that the obvious boundary, which differentiates tropical distribution, is located at an elevation of approximately 1,500 m, which separates the tropical rain forests from the evergreen broad-leaved forests; 2) that humid rain forests are found below 700 m elevation, mountain rain forests between 700 and 1,500 m, monsoon evergreen broad-leaved forests between 1,300 and 1,800 m and mountain mossy evergreen broad-leaved forests above 1,800 m. Non-representative mountain mossy dwarf forests (above 2,100 m) in the area are found on the windward sides and barren lands on mountain slopes; 3) that Hopea mollissima is one of the major component species of mountain rain forests, but it should not be considered as the major indicator species in humid rain forests as is generally accepted.  相似文献   

5.
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6.
Background： The Siberian moth （Dendrolimus sibiricus） （SM） defoliates several tree species from the genera Larix, Piceo and Abies in northern Asia, east of the Urals. The SM is a potential invasive forest pest in Europe because Europe has several suitable host species and climatic conditions of central and northern Europe are favourable for the SM.
Methods： This study developed a grid-based spatio-temporal model for simulating the spread of the SM in case it enters Europe from Russia via border stations. The spread rate was modeled as a function of the spatial distribution of host species, climatic suitability of different locations for the SM, human population density, transportation of moth-carrying material, and flying of moths from tree to tree.
Results and conclusions： The simulations showed that the SM is most likely to spread in the forests of northeast Belarus, the Baltic countries, and southern and central Finland. Climatic conditions affected the occurrence of the SM more than human population density and the coverage of suitable host species.  相似文献   

7.
Siberian moth Dendcrolimus superans sibiricus Tschetw. is the main important insect pest not only in Siberian coniferous taiga, but it often forms foci of mass reproduction in larch stands in the Russian Far East. This article has described outbreaks of the Siberian moth and other insect pests since 1960 till now.  相似文献   

8.
Douglas-fir (Pseudotusga menziesii (Mirb.) Franco), a native to the Pacific Coast Range in North America, is recognized as a tree that is long-lived and can grow rapidly to standing volumes that approach the highest recorded for temperate conifers. Managed plantations in western Oregon register maximum periodic annual increments (PAI) at ages between 20 and 40 years of ∼30 m3 ha−1 year−1. The same seed source, when planted in New Zealand and elsewhere in the Southern Hemisphere, may attain a PAI of ∼50 m3 ha−1 year−1. Is this higher productivity mainly related to climate or to isolation from native pests? To evaluate the role of climate, we obtained meteorological data from plantation sites in New Zealand and Oregon, from which we established relationships between mean monthly temperature extremes and solar irradiance, air humidity deficits, and frost frequency. Using these empirical relationships, long-term weather records were converted to the meteorological variables required to drive a process-based forest growth model, 3-PG, for sites approaching the most productive in New Zealand and in Oregon. Annual precipitation is similar in both areas, but sites in Oregon receive only 10% during the growing season, resulting in humidity deficits 30% larger than those recorded in New Zealand. According to sensitivity analyses and direct measurements, the more productive Douglas-fir forests in Oregon avoid the limiting effects of summer drought by obtaining water from the subsoil and fractured bedrock. If such forests were under a reduced evaporative demand similar to that in New Zealand, we show that they would exhibit comparable productivity.  相似文献   

9.
Vegetation dynamics of three forest communities were studied by resampling of relevés recorded in the 1970s in the Bohemian Forest (Šumava Mountains). Results of multivariate analysis (RDA) confirmed significant time changes in species composition of the climax (Calamagrostio-Piceetum) and waterlogged (Bazzanio-Piceetum) spruce forests. The changes in the sphagnum-rich waterlogged spruce forests (Sphagno-Piceetum) are close to the level of significance. The main vegetation changes are represented by a decrease in cover and/or frequency of hygrophilous or sciophilous species (e.g. Athyrium distentifolium, Oxalis acetosella) in climax spruce forests, and an abundant increase of species, indicating a preference to drier stands or better light conditions (e.g. Calamagrostis villosa, Vaccinium vitis-idaea or Avenella flexuosa), in waterlogged spruce forests. We also found a higher proportion of meadow species (e.g. Anthoxanthum odoratum, Festuca rubra or Luzula multiflora) in the newly recorded relevés from waterlogged forests. Analysis of species number per plot showed a remarkable shift to species-rich communities, especially in waterlogged stands.We tried to find the possible factors responsible for the observed changes. Unfortunately, only indirect measurement of environmental factors using Ellenberg’s indicator values could be used and did not yield sufficient results. Thus, the changes observed in climax spruce forests were ascribed mainly to a decrease in canopy cover, which was directly estimated. In waterlogged forests, a complex of several general factors, which influence the climax spruce forest, had to be taken into account, such as: (i) a decrease in atmospheric acidification during the last 10–15 years and subsequent improvement in soil conditions, especially in waterlogged stands; (ii) fragmentation of forests as a result of bark-beetles attack; (iii) climate warming documented by long-term local meteorological measurements.  相似文献   

10.
Sodium, potassium, magnesium, calcium and physicochemical parameters were monitored for one year in a mangrove tidal creek near Bragança, North Brazil, to determine their tidally induced and seasonal variations and the main parameters controlling the concentration of these cations. On a daily basis, cation concentrations showed a strong tidal rhythm due to the mixing of estuarine and mangrove waters. Mean concentrations were highest at the end of the dry season (December 1996) and lowest (April 1997) towards the end of the rainy season. Average values over one year were: Na+ = 329± 118mM, K+ = 6.9±2.5mM, Mg++=37 ±14 mM and Ca++= 6.9±2.4mM. Dissolved oxygen concentration was higher during the dry season due to enhanced aquatic primary production, with a maximum daily average value of 8.5mg/L in July 1996, and a minimum value of 4mg/L in June 1997. Cation concentrations were transformed relating them to the respective average values in standard seawater at salinity 35. Although cation concentrations and salinity tightly correlated, this standardization showed that the concentrations of K+, Ca++ and Mg++ did not depend solely on salinity and reflected the seasonal variation in aquatic primary production. It also allowed the discrimination of their sources (marine, riverine and groundwater). Thermodynamic equilibrium calculations indicate that phytoplankton may be regulating the concentration of these cations in the water column indirectly by inducing precipitation through pH increase and directly through metabolic uptake.  相似文献   

11.
lntroducti0nMan}'pIantshavFt1eshytYLlitsinALItumnil1teInperatezone.Thesefruit3providefoodtbrmanytYugivorouSbirds.BirdsgetnutritiontYomthetYuits,anddispersetheseedsofthesepIantsatthesametime.Manyre-searchesonthistopicaretinishedinMediterraneanScrubIandsand…  相似文献   

12.
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13.
The loess plateau in China is well-known for its severe water erosion. A nationwide soil erosion survey discovered that wind erosion of the loess land is also greatly concerned. The severity of wind erosion for each land use in Pengyang County of Ningxia Hui Autonomous Region, China, was evaluated according to the national standard of soil erosion classification. The evaluation system includes a GIS database, an evaluation indicator system and a classification system for land and land use. The erodible nature of soil and annual soil loss of the most erodible land were obtained as follows: (1) Croplands plowed and harrowed in late autumn were the most erodible land,with an erosion intensity of medium grade and an erodible proportion of 46%; (2) The erodible proportion of natural grasslands was between 19.3% and 21.5%, whose erosion intensity was of mostly tolerable grade; (3)When it came to the whole county, there was 21.3% of the total area in tolerable grade in terms of wind erosion intensity, 42.1% slight and 34.8% medium.  相似文献   

14.
We studied whether agrobiodiversity in home gardens reflects the cultural landscapes that embed them. We compared floristic composition, biomass and cover of trees in home gardens between the cultural landscapes on mountain slopes (MSL), small hills (SHL), and floodplains (FPL) in a segment of the Grijalva–Usumacinta watershed in the tropical lowlands of Tabasco, Mexico. We characterized the cultural landscapes based on information obtained through questionnaires, identified species and measured tree height and diameter at breast height in random samples of home gardens from two localities in each case. The cultural landscapes showed distinct land use combinations: MSL comprised subsistence agriculture, pasturelands and forests; SHL pasturelands, some secondary vegetation and industrial agriculture fields; and FPL mainly industrial agriculture fields and pasturelands. Total species richness was greater in MSL than in SHL and FPL. Mean species richness was greater in MSL and SHL (22.4 and 15.8 respectively) than in FPL (7.2), as was the mean number of individuals per home garden (98.2, 94.1 and 20.4. Dominant species in home gardens in FPL and SHL included particular secondary species for each landscape, whereas single or double occurrences of mature forest species were distinctive of home gardens in MSL. Mean biomass was greater in MSL than in SHL and FPL (37.1, 28.2 and 23.7 Mg C ha?1), as was tree cover (1.06, 0.95 and 0.76 m2/m2). We conclude that agrobiodiversity varies considerably among cultural landscapes and recommend the design of specific policies to enhance its conservation in each of them.  相似文献   

15.
Birch forests cover large areas of the northern Fennoscandia and the mountain birch (Betula pubescens ssp. czerepanovii) often forming the altitudinal and Arctic forest and tree lines. Interpreting the factors leading to landscape changes in mountain birch forest involves disturbance from anthropogenic use and climate as important factors. Using vegetation maps based on aerial photographs and satellite images from 7 years in combination with statistical data and ground estimation data of biomass in the period 1957–2006, we were able to assess the transitions among mountain heaths and different types of forest, the displacement of the altitudinal forest line and hence the change in biomass. The tree biomass as well as the growing stock for birch in Finnmarksvidda doubled in the period 1957–2006. Only lichen biomass has been significantly reduced in the period 1957 to 2000, with a subsequent slight increase of lichen biomass in the period 2000 to 2006. The results presented in this paper show significant and positive relationships between measured tree biomass and the increase in reindeer population in the period 1957–2006 in the study area. The hypothesis concerning the removal of the “lichen barrier effect” by heavy reindeer grazing which leads to increased success for birch seeds to germinate and sprout is therefore considered to be valid. However, also, climate change effects like increased precipitation, moth attacks, freezing and thawing events during winter and long-transported air pollution (e.g. nitrogen) may also have reinforced the changes in biomass. Climatic variables from regional weather stations for the period 1955–2006 did not, however, reveal any consistent change except for that the increased snow depth had a negative impact on the reindeer population while increase in snow depth hindering the reindeer in grazing seemed to have a positive impact on the lichen biomass. The ongoing development of increased forest cover and hence elevated forest line will lead to reduction of open habitats, and hence decreased grazing accessibility for the reindeer. The effects on forestry and carbon sequestration are also discussed, and here one of the suggestions is to let the northern birch forests act as carbon sinks contributing to the reduction of total net emission of CO2 in the Nordic countries. Land use like reindeer husbandry has shown to strongly affect relationships between ecological processes like tree-growth and climate. Moreover, reindeer husbandry is such a widespread human activity in the arctic and boreal region that it might affect the global carbon budget.  相似文献   

16.
Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values.However,the lack of genetic diversity background and related research hinders the development of conservation strategies.In this study,genetic diversity and distribution of five Larix species were investigated.Using 19 polymorphic microsatellite markers to study 272 representative individuals from13 populations,the results show low genetic diversity at the population level,with variation explained mainly b...  相似文献   

17.
Large scale harvest of Korean pine(Pinus koraiensis) seeds as a food product in the mixed Korean pine-hardwood forest of northeastern China poses a serious threat to the sustainability and restoration of this endangered regional ecosystem.Seed collection over past decades greatly reduced the seed bank and subsequent seedling and sapling recruitment,and impacting a wide array of granivorous animals that rely on the pine seeds.We surveyed Korean pine seeds,including solid seeds(SS),insect consumed seeds(ICS) and other(animal) consumed(OCS) kernels,of the seed bank(forest floor and the top 10 cm of mineral soil),the seedlings and saplings from 1 m 2 sample plots in five forest types in Liangshui Nature Reserve(LNR) of the southern Xiao Xing’an Mountains in northeastern China to provide accurate information for assessing the Korean pine regeneration potential.The average number of pine seeds in the seed bank were 11.2 seeds/m 2,9.1 seeds/m 2,4.6 seeds/m 2,1.1 seeds/m 2,and 0.2 seeds/m 2 in Korean pine-basswood forest,mixed Korean pine-hardwood forest,mixed conifer-hardwood forest,white birch forests,and oak forests,respectively.In the first three forest types,percentages of SS(potentially viable seeds) were 11.2%,3.5% and 27.8%,respectively.The percentages of ICS(not viable seeds) were consistent at around 35%.The higher but variable percentages of OCS(not viable seeds) indicated high seed predation in these forests.Compared with other studies,we recorded higher percentages of seed damage,probably due to our survey approach and the increased depth of seed bank sampled in our study.Depletion of pine seeds in the seed bank greatly reduced seedling and sapling recruitment.Densities of pine seedlings varied from about 180 trees/ha in the mixed Korean pine-hardwood forest to about 5,400 trees/ha in the mixed conifer-hardwood forests and showed a high degree of spatial variation.Saplings were rare in the mixed Korean pine-hardwood forest,but ranged in the thousands in other forests.Large scale pine seed harvest has seriously threatened the sustainability of the mixed Korean pine-hardwood forest ecosystem.Scaling down the seed harvest or supplemental planting of pine saplings are urgently needed to maintain the health of the existing Korean pine forests and to restore this endangered ecosystem.  相似文献   

18.
概述了近20年来国内外对催化α-蒎烯氧化反应过程的研究,重点分析了α-蒎烯氧化中催化剂的性能特点及产物分布规律,总结了过渡金属盐、氧化物、配合物、分子筛及杂多酸在α-蒎烯氧化中的催化作用,比较了催化活性及选择性的特点,并初步探讨了发展趋势.提出在已有的α-蒎烯氧化反应催化剂中,分子筛类催化剂在制备方法和工业化发展上有一定的优势,深入研究过渡金属化合物在α-蒎烯氧化反应的催化性能及调变方法,应是α-蒎烯氧化反应中值得重点关注的研究内容.  相似文献   

19.
Plant distributions are thought to be controlled by climate at large scales, and by non-climatic factors including soil conditions, topography and biotic interactions at smaller scales. However, not all plant distributions are explained by the current environment. Lags between current plant distributions and suitable environment for them are suggested to exist, which is often called empty habitat. To identify the existence and cause of lags between current climate and the distribution of Tsuga diversifolia, climatic conditions for the species distribution were clarified and potential habitats under current and the last glacial maximum (LGM; 21 ka) climates have been projected. The relationships between T. diversifolia distribution and climatic variables were explored using a classification tree model and a generalized additive model based on high-resolution (ca. 1 km) climatic data and a nationwide distribution database. The models were highly accurate. We revealed that T. diversifolia requires high summer precipitation even in humid Japanese environments. Areas with cool and wet summers were classified as potential habitat. Empty habitat for the focal species was identified in Hokkaido. Meanwhile, no potential habitat was projected in Hokkaido under the LGM. Additional experiments that varied temperature and summer precipitation during the LGM showed that the potential habitat was projected in Hokkaido irrespective of temperature decrease if summer precipitation increased nearly equal to the current climate. These results suggest that T. diversifolia vanished from Hokkaido, where fossil evidence indicated its occurrence until the late Neogene, during the glacial periods of the Pleistocene because of increased summer dryness.  相似文献   

20.
The 1998 floods in China triggered the implementation of the Natural Forest Conservation Program (NFCP) which includes: (i) a logging ban over state-owned natural forests in order to protect the deteriorating natural environment, and (ii) strategies for the establishment of commercial plantations and relocation of laid-off forest workers, with the aim of mitigating the negative socioeconomic impacts of the logging ban. In this paper, Sichuan province is used as a case study to analyze the disincentives faced by local communities in developing commercial plantations and the institutional failure to address the disincentive issue. Insight on the necessity of 'real participation' of local communities has been provided, and ways to create incentives as well as institutional rearrangement has been explored and recommended.  相似文献   

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