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1.
The canopy structure of Erica umbellata was studied in order to (a) quantify biomass allocation among several organ types, (b) analyse the possible changes in vertical structure related to season and plant size, and (c) evaluate the effectiveness of non-destructive measures to estimate biomass for a species that is declining in some areas, due to fire and other human disturbances. The study was conducted in NW Spain, sampling E. umbellata plants belonging to three size groups. Destructive (biomass) and non-destructive (frequency, height, diameter) measures were used to characterise the vertical distribution and abundance of photosynthetic, woody, reproductive and dead organs. Allometric equations were calculated to estimate total mass using non-destructive measurements. As E. umbellata increases in size, those organs with a higher renewal rate (leaves, new stems, flowers) increase in the upper strata. Seasonal differences are recorded for the reproductive organs and new stems. A sharp decrease in the green/total phytomass ratio (from 0.51 to 0.17) is observed as plant size increases. Organ biomass can be accurately predicted from total weight and it is also possible to estimate the total weight from non-destructive measures, which provides an easier way of recording data in the field.  相似文献   

2.
The carbon balance in reproductive organs over the whole reproductive period was estimated for 20 woody species on the basis of the published data on the final dry weight and CO2 exchange of reproductive organs. The relationship between net respiration and dry weight growth was formulated by a linear function with a negative y-intercept. From this linear relationship, linear relations of dry weight growth and net respiration to net translocation were derived. The size dependence of net respiration showed that the net respiration changed from negative to positive as the final dry weight of the reproductive organ exceeded 0.481 g. The cost for translocation per unit dry weight was much lower in the species with small reproductive organs (<0.481 g) because of their photosynthetic contribution to the weight growth. The relation of dry weight growth/net translocation ratio to net translocation was expressed as a hyperbolic function. The dry weight growth/net translocation ratio remained at 0.650, in the higher range of net translocation, irrespective of woody species. Electronic Publication  相似文献   

3.
Bana, or Low Amazon Caatinga is an evergreen sclerophyllous woodland. It occurs on bleached quartz sands in the lowlands of SW Venezuela, where it occupies relatively small ‘islands’ amidst Tall Amazon Caatinga which is exclusively developed on tropaquods. There is an outer vegetation belt about 20 m in width in which trees over 10 m in height occur (Tall Bana); its structure and floristic composition resemble Tall Amazon Caatinga. Low Bana (maximum tree height usually below 5 m) follows next. The central part is occupied by Open Bana in which even lower trees are very widely spaced. Destructive phytomass sampling was carried out for chemical analyses in seven plots along a 150 m line across the zonation. The total dry matter of living plants including roots of Tall Bana (30–32 kg/m2) compares rather well with 41 kg/m2 in Tall Amazon Caatinga. This is only 9–14 kg/m2 in Low Bana, and 4–6 kg/m2 in Open Bana. The average root % of total phytomass increases from 41% in Tall Bana to 63% in Low Bana, and is 88% in Open Bana. Average total dry dead above-ground phytomass (including standing trees and stumps) declines from 1 kg/m2 in Tall Bana to 0.2 kg/m2 in Open Bana. An accumulation of dead matter in Low and Open Bana, relative to the above-ground phytomass of living plants, is noted and this contrasts with the general absence of raw humus in the soil. Eighty-two species of woody plants (dbh≥1 cm) were recorded on the total plot area (640 m2); 90% of the species are also known to occur in Tall Amazon Caatinga. The species number declines from 59 in Tall Bana to 18 in Open Bana. Mesophylls sensu strictu dominate in Tall Bana, while notophylls are dominant in Low and Open Bana. Herbaceous species are less numerous: most of them belong to the Araceae, Bromeliaceae, Orchidaceae, Droseraceae, Eriocaulaceae and Xyridaceae.  相似文献   

4.
Phyto- and necromass above and below ground in a fen   总被引:3,自引:0,他引:3  
Hugo Sjörs 《Ecography》1991,14(3):208-218
Few investigations deal with the subterranean phytomass in fens (minerotrophic peatlands), their results differing widely. This study was carried out in a "rich fen" in central Sweden, and involved excavation of peat monoliths, depth-sectioning and hand-sorting as to species, type of organ, and living or dead condition. The below-ground living phytomass was large, over 4 kg m−2 in each of two sample plots, being no <97–96% in the dominants, Carex limosa and C. lasiocarpa , 89% on average in Menyanthes trifoliata , and c. 93% for all species. Carex limosa had its rhizome maximum slightly higher than C. lasiocarpa , but a greater part of its roots penetrated deeper. For Menyanthes , also net annual production above and below ground was estimated. The subterranean phytomass decreased with depth, but living roots were found even at 42 cm. The recognizable necromass did not decrease with depth. These recent constituents would render a very unequal age to the peat. The imbalance between the small green aerial phytomass and the much greater subterranean phytomass was emphasized. It could be related to a relatively very great translocation of photosynthates from above to below ground, and/or to longevity of below-ground organs, the latter at least in Menyanthes.  相似文献   

5.
Our objective was to asses site parameters, species diversity, phytomass structure and element stores of a Terra-firme forest prior to subsequent studies on nutrient fluxes during forest conversion. The soil was classified as a Xanthic Ferralsol, with a low effective cation exchange capacity (ECEC), low nutrient status and a deeply weathered solum. On 0.75 ha, including all trees with a DBH >7 cm, we identified 222 tree species belonging to 58 families. The above-ground phytomass was estimated using logarithmic regression analysis on two plots of 0.25 ha each. Despite differences in forest structure and species composition, no major differences were found in terms of total phytomass or overall element stores. The mean living above-ground phytomass (LAGP) was 257 Mg ha–1, and mean quantity of litter 14 Mg ha–1, while dead wood contributed between 10 to 17% of total above-ground phytomass (32–56 Mg ha–1). Element store in LAGP was medium to high compared to other studies on tropical forest systems, while LAGP itself was comparatively low. Comparing 26 humid tropical forest stands recorded in literature, no correlation was found between LAGP and the amount of N and base cations stored in LAGP. However, a correlation between LAGP and P storage in LAGP (R 2=0.76) indicates the important role P may play in phytomass accumulation on zonal tropical soils. More then 60% of C, 20% of total N, 10% of total P and 66–88% of total K, Ca and Mg of the system (including the first meter of soil) were concentrated in the above-ground phytomass, including deadwood and litter. Consequently, phytomass destruction in form of forest conversion will lead to major element losses from the system.  相似文献   

6.
海南岛霸王岭热带季雨林树木的死亡率   总被引:2,自引:0,他引:2       下载免费PDF全文
树木死亡是调节群落组成和结构的一种方式, 在森林生态系统动态中发挥着重要作用。该文在对海南岛霸王岭热带季雨林群落大量调查和树种功能群划分研究的基础上, 探索了热带季雨林群落及其不同功能群树木的死亡率及其随径级和环境条件的变化规律。结果表明: 海南岛霸王岭热带季雨林群落内树木死亡率的变化范围为3.42%-18.71%, 平均值为7.60%。按照功能群比较, 乔木死亡率显著高于灌木, 落叶树种死亡率高于常绿树种, 但具刺树种死亡率显著低于无刺树种。按照树木径级划分, 5-30 cm径级范围的死亡率均超过10%, 最高值出现在5-10 cm径级范围, 在相同径级范围内比较时, 落叶树种在 胸径(DBH ) < 5 cm时的死亡率显著高于常绿树种, 而在其他径级范围内, 二者之间无显著差异, 具刺和无刺树种的死亡率在所有径级范围内均无显著差异。乔木死亡率与群落距河流距离具有显著的相关性, 距离河流越远死亡率越高; 落叶树种和无刺树种则与坡位存在显著的相关性, 坡上部的死亡率显著高于坡中部。热带季雨林内树木的死亡率与其所处的群落生境有关, 较干旱的生境是导致树木死亡率较高的重要原因。  相似文献   

7.
Phytomass structural characteristics are highly related to vegetation flammability. In fire-prone species like Mediterranean gorse, which accumulate standing dead fuel, susceptibility to fire is a function of fuel load, vegetation composition and fuel cover, and these characteristics change with time. Thus, for effective fuel control management, knowledge of the vegetation structural dynamics related to fire risk is crucial for preventing future fires. This study analyses structural dynamics in the above-ground phytomass of Ulex parviflorus shrublands in relation to different stages of flammability, i.e., the amount of time elapsed since the last fire. For this, 152 plants were cut from shrublands at different stages of development (young, mature and senescent), and various dimensional measurements were taken on each. The phytomass was separated into living or dead fuel fractions as well as into twigs or branches depending on the stem diameter. Basal diameter is the variable that best predicted Ulex parviflorus total phytomass as well as that of the different fractions. Both dimensional and phytomass variables increased with plant development. In the young shrublands Ulex parviflorus constitutes 54% of total phytomass, and Ulex parviflorus's dead twigs fraction accounts for 5% of total phytomass. In the mature and senescent shrublands, this species represents 80% of total shrubland phytomass, and dead twigs reach values greater than 40%. Our results show that structural changes in the fuel over short periods of time (young and mature) reveal critical periods in shrub development. Identification of these stages is a necessary tool for planning fuel control programmes.  相似文献   

8.
Ecological studies were made on the structure and phytomass of the secondary coppice forest near Tokyo, which was dominated by a deciduous oak,Quercus serrata Thunb. Average height of dominant trees was about 10 m. The shoot density at the beginning of the study was 4,600 ha−1 of which 89.5% belonged toQ. serrata. During the subsequent two growing seasons 8.3% of shoots, mainly small ones, died. All the tree shoots in a 10 m×10 m quadrat were cut and most of the underground parts were dug out. The phytomass calculated by the allometric relations of the dry weight of each plant organ to the square of DBH (D 2) agreed fairly well with the values directly weighed. The average phytomass of the overstory trees was 906 kg a−1. The leaf area index (LAI) of the canopy was 3.85. Phytomass of the undergrowth, mainly a dwarf bamboo,Pleioblastus chino Makino, was 91.8 kg a−1 with LAI of 3.46. The dead phytomass in the stand was 177 kg a−1, so the phytomass alive and dead amounted to 1,170 kg a−1. Heavy self-thinning of the coppice forest is discussed in relation to the rapid development of the log-normal distribution of tree sizes and to the large allometric constants for leaf and branch weight toD 2.  相似文献   

9.
Kamoi T  Kenzo T  Kuraji K  Momose K 《Oecologia》2008,154(4):663-677
Excess flower production is a common phenomenon in hermaphrodite plants. The tropical pioneer shrub Melastoma malabathricum (Melastomataceae) frequently aborts not only young ovaries just after flowering, but also flower buds and developed ovaries. We tested a hypothesis that the excess production of reproductive organs and their abortion in this species is an adaptation to environmental fluctuations over shorter time scales than had previously been reported in other plants. To calculate the daily demand for carbohydrate and water by reproductive organs at the level of individual plants, we measured the respiration and transpiration of the reproductive organs at various stages and monitored their growth and abortion. To determine the daily supply of carbohydrate and water, we measured the photosynthetic productivity of leaf area, solar radiation and rainfall. The daily carbohydrate demands of the reproductive organs were significantly correlated with total photosynthetic productivity per leaf area during the previous 1, 3 and 5 days, but no correlations were found between the demands for water and accumulated rainfall or radiation. The daily abortion rates of the population were also correlated with demand for carbohydrates on the previous day per total photosynthetic productivity per leaf area. In brief, it was considered that this species produced and grew more reproductive organs when more resources were supplied and that the abortion occurred when demands for carbohydrate were large. Therefore our hypothesis was supported. We concluded that this reproductive strategy was an adaptation for pioneers characterized by continuous reproduction in aseasonal tropics. In our study, the adaptive consequence of excess production was determined by measuring natural environmental fluctuation.  相似文献   

10.
紫茎泽兰的CO2交换特性   总被引:14,自引:5,他引:9  
紫茎泽兰是一种外来入侵有害植物,从CO2交换特性角度研究其入侵特性的报道较少。对其生殖器官(花和果)和营养器官(茎杆和根系和不同生长条件下的叶片)气体交换特性进行了测定,并与8种本地种和已报到的世界主要草本和木本植物的光合速率、呼吸速率进行了对比。在结果中观察到,不同叶片的净光合能力和呼吸速率差异较大,同一茎杆不同叶片、不同年龄株丛和同一株丛不同年龄分株上叶片、不同生境内嫩叶、成叶和老叶、不同长度节间上生长叶片以及基生叶和顶生叶光合能力都受到气孔限制和非气孔限制(羧化能力)的影响,但不同叶片所受的限制程度不同。综合来看,最大叶片净光合速率为17.6μmol·m-2s-1,分布最集中的区域为11~15μmol·m-2s-1,占所有观测值的50%,而叶片暗呼吸速率70%以上的观测结果在1~3μmol·m-2s-1之间,分布最集中的区域在1.5~2.0μmol·m-2s-1,占所有测定值的40%。生殖器官具有较高的代谢机能,其中幼嫩花蕾的呼吸速率高达37μmol·kg-1DWs-1,其呼吸速率平均比茎杆和根系高出4倍。而且,花蕾、成花和幼果都具有较高的光合能力(毛光合速率分别约为40,16μmol·kg-1DWs-1和11μmol·kg-1DWs-1,是对应呼吸速率的110%,68%和74%),对照同一时期(早春:旱季生殖生长季)的叶片光合能力仅为营养生长季节(夏季)的1/3,生殖器官这种光合作用是对叶片光合能力不足的一种补充。茎杆和根系呼吸速率与直径的关系相似,即直径越小,呼吸速率越高。直径小于0.5mm的根系和茎杆的呼吸速率都在11μmol·kg-1DWs-1以上。与其他植物比较,在温度和根系大小相当的情况下,紫茎泽兰与其它根系呼吸比较并没有明显区别。与已报道的草本植物和木本植物光合呼吸范围来看,紫茎泽兰叶片光合速率介于草本植物系统的中等偏下,位于木本植物系统的中等偏上,而其呼吸速率和草本植物相当但明显高于木本植物。与本地其他伴生植物比较,紫茎泽兰光合能力与本地常绿阔叶树种、落叶阔叶树种相当,而明显高于常绿针叶树种,但与同一时期的草本植物光合能力相当甚至偏低。其呼吸速率与本地草本和木本植物相差不明显。因此,不同生境下和不同生长状态的紫茎泽兰的光合和呼吸速率都具有较强的可塑性,这种可塑性可能有利于其定居不同的生境,即在适宜生境保持最高的光合能力和呼吸代谢水平,利于快速入侵,而在胁迫生境下以避免消亡为主,待机爆发。但是,仅通过比较紫茎泽兰与其它植物的叶片光合速率和呼吸速率不容易判断这一植物的强入侵能力。  相似文献   

11.
The dynamics of aboveground big woody organs over 10 cm diameter was studied at a mature foothill dipterocarp forest in West Sumatra. The biomass of big woody organs was estimated to be 519 m3 ha−1 or 408 metric ton ha−1 by means of a pipe model theory. The diameter distribution showed a convex curve and the mode was found at a diameter of about 20 cm. The standing mass of big dead woody litter on the forest floor was 116 m3 ha−1, which accounted for 22% by voume or 9.5% by weight of the biomass of living organs respectively. Thedbh observation with two 1-ha plots for 4 yr and 5 yr respectively revealed that the average net production rate was 9.5 ton ha−1 yr−1. The death rate (7.9 ton ha−1 yr−1) accounted for 83% of the net production rate and was nearly equivalent to the decay rate (7.5 ha−1 yr−1) of dead wood on the forest floor. The balance between the death and decay rates was confirmed for each diameter class. Average turnover periods for big woody organs and dead woody litter were estimated to be 43 and 8.1 yr, respectively. Standing masses of live anddead woody materials accumulated in the study forest were approximately equal to those obtained in a mature tropical lowland rainforest, whereas the flow rates were lower, being only 70% of the corresponding values.  相似文献   

12.
Abstract. Spatial and temporal soil partitioning between roots of the two savanna plant components, i.e. trees and grasses, were investigated in a West African humid savanna. Vertical root phytomass distribution was described for grass roots, large (> 2 mm) and fine (< 2 mm) tree roots, in open sites and beneath tree canopies. These profiles were established monthly over one year of vegetation growth. Natural 13C abundance measurement was used to determine the woody/herbaceous phytomass ratio in root samples. Tree and grass root distributions widely overlapped and both were mostly located in the top 20 cm of the soil. Grass root phytomass decreased with depth whereas woody root phytomass peaked at about 10 cm depth. No time partitioning was detected. These structural results do not support the hypothesis of soil resource partitioning between trees and grasses and are thus consistent with functional results previously reported.  相似文献   

13.
Abstract. This paper describes patterns of below-ground components in grassland ecosystems. It provides estimates of the contribution of below-ground organs to the total phytomass of the community and of different species to the below-ground phytomass; it describes the distribution of above- and below- ground organs of different species and the spatial and temporal correlation between above-ground and below-ground phyto-mass – both total standing crop and net primary production. 10 Siberian grasslands (meadows and steppes) were investigated during 15 yr. Ca. 70 % of the living phytomass is located in the soil and no less than 70 % of the net primary production is allocated in below-ground organs. Phytomass distribution in the soil layer is more homogeneous than above-ground. For some species the spatial distribution within 1-m2 plots of the green and below-ground phytomass is similar, for others it is quantitatively or qualitatively different. According to the dominance-diversity curve, the above-ground size hierarchy is much stronger than the below-ground one. The active growth of above- and below-ground organs of a species may occur at different times of the season and it varies from year to year. Allocation of organic substances to rhizomes and roots occurs simultaneously and with proportional intensity.  相似文献   

14.
Protected areas such as forest reserves are often assumed to be best ways to conserve biodiversity and maintain intact ecosystems. We examined woody plant composition and diversity in the gallery forest and savannah woodland habitats of Amurum Forest Reserve and areas immediately surrounding it in Jos, Nigeria. A total of 100 10 × 10 m sample plots were established inside and outside the reserve. All woody plants ≥1 cm diameter at breast height (dbh) were identified and measured. A total of 7,564 individual plants categorized as 134 species from 44 families were recorded. Overall species diversity was significantly higher in the Forest Reserve than outside the reserve, although more species were encountered outside the reserve. Our findings suggest that, protected areas and the areas surrounding them are important for the conservation of biodiversity as the areas outside protected areas also contain species of conservation value. The continuous degrading areas outside protected areas isolates them and poses a serious threat to the long‐term viability of wildlife populations, so it is important that biodiversity in protected areas and their surrounding areas be conserved.  相似文献   

15.
Estimations were made of the vertical gradient of transpulmonary pressure (VGTP) from measurements of esophageal pressure in nine head-up dogs at functional residual capacity (FRC) when alive, when dead, and after total bilateral pneumothorax. The VGTP of 0.4 cmH2O/cm height in the alive state was abolished by pneumothorax, and roentgenograms showed that the heart moved in a caudal-dorsal direction. There was a small but significant increase in the VGTP on going from FRC to near total lung capacity (TLC) in alive head-up dogs. In eight dead head-up dogs heart weight was increased by replacing various amounts of heart blood with Hg. The VGTP was significantly increased from 0.28 to 0.51 cmH2O/cm height. The fractional increase in the VGTP was similar to the fractional increase in heart weight. In five dogs extrapolation to zero heart weight gave an average VGTP of 0.14 cmH2O/cm height. We conclude that the lungs help support the heart in the head-up dog and that the VGTP is in part determined by the pressure distribution required for this support.  相似文献   

16.
Knowledge of vegetation dynamics associated with human land-use change and environmental variables is crucial for sustainable watershed management. The objective of this study was to analyse woody plant diversity in response to the effects of anthropogenic disturbances, and topographic variables in different land-cover types. Woody plants ≥5 cm diameter at breast height (DBH) were recorded from 20-by-20 m plots, those <5 cm DBH were recorded from 10-by-10 m plots, and tree seedlings were recorded in 3-by-3 m plots. Nonmetric multidimensional scaling with Bray–Curtis distance was employed to analyse woody species composition. Woody species richness was analysed using generalised linear modelling. Tree diameter-class distributions were examined for population structure. The study identified 104 woody plants belonging to 52 families, where 74.5% were indigenous and 16.7% were endemic to Ethiopia. Asteraceae, Fabaceae and Rosaceae were the most species-rich families. There was evidence for the effect of anthropogenic disturbance and elevation on woody species composition. Wetlands contained the highest woody species richness, while woody species richness declined with increasing elevation and disturbance. Evidence of good regeneration was observed in wetlands. To sustain the ecological functions and services provided by the watershed, rehabilitation of the forest and shrub-cover should be a high priority for local management authorities.  相似文献   

17.
The natural forest of Masha was studied to determine the species composition and population structure of woody species in the area. A total of 130 plant species belonging 61 families were recorded, in which family Acanthaceae was represented by 11 species followed by Rubiaceae (10) and Asteraceae (9). The composition and population structure of woody species, with diameter at breast height (DBH) >2.5 cm and height >2 m, and their regeneration were assessed in 65 sample plots of 400 m2 each. The density for trees and shrubs with DBH >2.5 cm was 1681 ind.ha?1, and the basal area of the study area was 142.6 mha?1. Four community types were recognized. This forest is of international and national conservation importance given its high biodiversity. Managing the remaining forest would be an appropriate option for sustainable management of biodiversity.  相似文献   

18.
以内蒙古锡林河流域沿水分梯度分布的灰脉苔草(Carex appendiculata)、贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、小叶锦鸡儿(Caragana microphylla)和冷蒿(Artemisia frigida) 6个草地群落为对象, 研究了围封禁牧与放牧样地中144个共有植物种的高度、丛幅面积、茎、叶和株(丛)生物量、茎叶比等性状。结果表明: 1)在个体水平上, 放牧样地中植物的生殖枝高度、营养枝高度、丛幅面积、单株(丛)生物量、茎、叶生物量和茎叶比均显著低于围封禁牧样地, 植物在放牧干扰下表现出明显的小型化现象; 2)在群落水平上, 放牧亦显著降低了群落总生物量和茎、叶生物量; 3)过度放牧显著改变了物种的资源分配策略, 使生物量向叶的分配比例增加, 向茎的分配比例减少。资源优先向同化器官分配可能是植物对长期放牧干扰的一种重要适应对策; 4)轻度放牧对物种的资源分配没有显著影响, 单株(丛)生物量和群落茎、叶及总生物量均表现出增加趋势, 这与过度放牧的影响正好相反。过度放牧引起的植物个体小型化改变了生态系统中物种的资源分配策略, 进而对生态系统功能产生重要的影响。  相似文献   

19.
The woody species richness patterns in three 2–4 km long transects, approximately 1–3 km apart in a lowland (600–700 m) dryland around Lokapel in Turkana northern Kenya was analyzed in 2003 at 200–500 m intervals using the Point-Centred Quarter (PCQ) method involving 51 observation points. Transect 1 and 2 were set along ephemeral runoff channels locally known as lagga with wet season flow westwards from the Lokapel Hills to the Turkwell River. Transect 3 was a cross-cutting profile dissecting the area initially downhill from the Lokapel Hills and later gently uphill eastwards towards Lokichar. The altitude at each of the 51 observation sites was recorded using a GPS and the woody species identified through local knowledge and taxonomic aids. The results showed that the overall integrated altitudinal gradient for the three transects was approximately 100 m. A total of 43 species of trees and shrubs were identified. The Shannon index showed that Transect 2 had the highest diversity of woody species followed by Transect 1 and Transect 3 while the Sorensen’s index indicated qualitative dissimilarity between all the transects. The results of regression analysis indicated that woody species richness increased linearly with elevation in only one transect but regression analysis of height of woody plants and altitude indicated that only about 20% of the variation in the height of woody plants was accountable by altitude. The spatial analysis of woody species-richness and altitudinal gradient showed a dual peak pattern with the main richness peak in low lying areas below 700 m which was mainly within or close to the riparian floodplain environment of the Turkwell River. A minor richness peak was also identified in higher lying areas around the Lokapel hills. The species richness pattern was similar to the hump-shaped altitudinal species-richness pattern which has been recorded widely around the world but mainly in large-scale studies.  相似文献   

20.
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