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1.
Heiser  Charles 《Economic botany》1978,32(3):222-236
Economic Botany - The totora (also known as matara and merme),Scirpus californicus, is widely used in Ecuador and Peru for a number of purposes. Floats made from it are still found at L.ake San...  相似文献   

2.
Juncus arcticus var. andicola is native to the Andean region. Its stems are used to make handicrafts by the rural mestizo population of Cotopaxi province in Ecuador. These products are sold at traditional markets along the Andes of Ecuador. The plant is of great economic importance in the modest lives of the artisans. Totorilla has been cultivated by this rural population. It is cultivated in pools and sometimes wild populations are managed. The area of production is 1.5 ha. One woven item can be made from a 0.35 m2 totorilla stand area. A 100 m2 yielded 850 woven items annually, bringing in a gross income of U.S. $1275 per year, corresponding to 66% of the official minimum salary in Ecuador. The plant also provides a good source of cattle fodder during periods of drought.  相似文献   

3.
We studied vegetation changes in a small floating mat bog in Mizorogaike Pond (Kyoto, Japan), which had experienced a severe decrease in the number and area of hummocks caused by nutrient loading in the 1960s and 1970s, to examine whether reducing the extent of nutrient loading can restore degraded wetland vegetation. However, nutrient loading in the region has been minimized since the 1980s. We examined the distributions of hummocks and Sphagnum cuspidatum mats in 1980, 1988, and 2006, as well as nine major vascular plants that dominated the hollows on the floating mat in 1980 and 2006. The total area of normal hummocks formed by Sphagnum palustre increased from 5865.3 m2 in 1980 to 5913.6 m2 in 1988 and 8485.2 m2 in 2006. The total area of the S. cuspidatum mats also changed, from 416.4 m2 in 1980 to 322.3 m2 in 1988 and 1012.5 m2 in 2006. Examination of the spatial distribution patterns of major plants revealed that emergent plants decreased in the northern part of the mat, but increased in the southern part. Thus, the improved pond water quality was effective at restoring hummocks, although nutrient loading may have caused some irreversible changes in the wetland vegetation.  相似文献   

4.
Various types of sub-aerially exposed microbial mats, including emergent mats, beach sand, beach rock and Kopara mats, are widespread on the 78 km (25 km2) of rim surrounding the Tikehau atoll lagoon. These mats form laminated accretions or diffuse microbial communities growing under high insolation and temperatures, and are therefore subject to desiccation. Both heterocystous and non-heterocystous cyanobacteria occur in these mats. Using acetylene reduction techniques, nitrogenase activity was observed at all sites over a period of 5 years and was 3–17 times higher during daylight than at night in all communities except for beach rock. 15N2 measurements indicated a molar ratio of acetylene reduction to N2 fixed of 1.6 for all exposed communities. Estimated N2 fixation ranged from 1.44 to 8.0 mg N m−2 day−1 in these exposed communities (mean of 4.66 mg N m−2 day−1) with beachrock showing the highest rates. For the whole reef rim, daily N2 fixation amounted to 98.42 kg N day−1 which represents 28% of the rate of fixation in the entire lagoon (area 400 km2).  相似文献   

5.
Canopy transpiration in a chronosequence of Central Siberian pine forests   总被引:4,自引:0,他引:4  
Tree transpiration was measured in 28, 67, 204 and 383‐y‐old uniform stands and in a multicohort stand (140–430 y) of Pinus sylvestris ssp. sibirica Lebed. in Central Siberia during August 1995. In addition transpiration of three codominant trees was monitored for two years in a 130‐y‐old stand. All stands established after fire. Leaf area index (LAI) ranged between 0.6 (28‐y‐old stand) and 1.6 for stands older than 67‐y. Stand xylem area at 1.3 m height increased from 4 cm2 m?2 (28‐y) to 11.5 cm2 m?2 (67‐y) and decreased again to 7 cm2 m?2 in old stands. Above‐ground living biomass increased from 1.5 kg dry weight m?2 (28‐y) to 14 kg dry weight m?2 (383‐y). Day‐to‐day variation of tree transpiration in summer was dependent on net radiation, vapour pressure deficit, and soil water stress. Tree‐to‐tree variation of xylem flux was small and increased with heterogeneity in canopy structure. Maximum rates of xylem flux density followed the course of net radiation from mid April when a constant level of maximum rates was reached until mid September when low temperatures and light strongly reduced flux density. Maximum sap flux density (60 g m?2 s?1) and canopy transpiration (1.5 mm d?1) were reached in the 67‐y stand. Average canopy transpiration of all age classes was 0.72 ± 0.3 mm d?1. Canopy transpiration (E) was not correlated with LAI but related to stand sapwood area SA (E = ? 0.02 + 1.15SA R2) which was determined by stand density and tree sapwood area.  相似文献   

6.
Earthworm communities were studied at six heap sites representing a chronosequence of Alnus glutinosa (black alder) stands (age 3–62 years) and compared with those on an unameliorated heap and in an alder stand (60 years old) on natural soil. Spoil heaps in the open‐cast coal mining area near Sokolov (northwestern Bohemia) were mainly reclaimed using afforestation. No earthworms were found on the virgin heap. Young plots were colonized by euryecious epigeic earthworms (i.e., those living above soil surface), but higher proportions of endogeic species (i.e., soil dwellers), did not appear until after more than 30 years of succession. The density and biomass of earthworms increased from the youngest stand (67 individuals/m2; 5 g/m2) to the older ones (e.g., 407 ind/m2; 13 g/m2 in the 23‐year‐old stand). However, both parameters were low in the oldest stand (35 ind/m2; 3 g/m2), but this may have been the result of extensive soil disturbance. Earthworm populations were often higher in reclaimed sites than in the control alder stand (150 ind/m2; 7 g/m2). However, the community structures were different, with the control being dominated by the litter‐feeding species, Dendrobaena vejdovskyi.  相似文献   

7.
Abstract Leaf area index (LAI) is a key parameter controlling plant productivity and biogeochemical fluxes between vegetation and the atmosphere. Tropical forests are thought to have comparably high LAIs; however, precise data are scarce and environmental controls of leaf area in tropical forests are not understood. We studied LAI and stand leaf biomass by optical and leaf mass-related approaches in five tropical montane forests along an elevational transect (1,050–3,060 m a.s.l.) in South Ecuador, and conducted a meta-analysis of LAI and leaf biomass data from tropical montane forests around the globe. Study aims were (1) to assess the applicability of indirect and direct approaches of LAI determination in tropical montane forests, (2) to analyze elevation effects on leaf area, leaf mass, SLA, and leaf lifespan, and (3) to assess the possible consequences of leaf area change with elevation for montane forest productivity. Indirect optical methods of LAI determination appeared to be less reliable in the complex canopies than direct leaf mass-related approaches based on litter trapping and a thorough analysis of leaf lifespan. LAI decreased by 40–60% between 1,000 and 3,000 m in the Ecuador transect and also in the pan-tropical data set. This decrease indicates that canopy carbon gain, that is, carbon source strength, decreases with elevation in tropical montane forests. Average SLA decreased from 88 to 61 cm2 g−1 whereas leaf lifespan increased from 16 to 25 mo between 1,050 and 3,060 m in the Ecuador transect. In contrast, stand leaf biomass was much less influenced by elevation. We conclude that elevation has a large influence not only on the leaf traits of trees but also on the LAI of tropical montane forests with soil N (nitrogen) supply presumably being the main controlling factor.  相似文献   

8.
Ficus lacunata Kvitvik, a new species of subgen.Pharmacosycea sect.Pharmacosycea collected in the provinces of Carchi, Imbabura, and Pichincha in Ecuador, shows affinities to bothFicus macbridei Standl. andFicus tonduzii Standl. but differs distinctly in leaf and syconium characters.  相似文献   

9.
Leaf area index (LAI, the one-sided foliage area per unit ground surface area) is a key determinant of plant productivity which has a large influence on water and energy exchange between vegetation and the atmosphere. The variation in forest LAI across landscapes and environmental gradients and its causes are not sufficiently understood. We measured the LAI of European beech (Fagus sylvatica) by litter trapping in 23 closed, mature stands across gradients of rainfall and soil acidity or fertility. With a mean LAI of 7.4 m2 m−2 (minimum: 5.6, maximum: 9.5 m2 m−2), beech stands maintained a comparably high leaf area index with relatively small variation along steep environmental gradients. Contrary to expectation, decreasing water availability (rainfall gradient from 1030 to 520 mm yr−1) or increasing soil acidity (pH 3–7) had no significant effect on LAI. Stand leaf mass (M l) increased slightly with soil fertility (C/N ratio, base saturation). We regressed parameters of site water availability (rainfall), soil fertility or acidity (pH, base saturation, C/N ratio, exchangeable Mg and Al content), and stand structure (stand age and stem density) against LAI and M l in order to detect environmental controls of stand leaf area. Stand age was the most influential factor for both LAI and M l (negative relationship). Stem density and the base saturation of the soil affected M l significantly, but had a weak influence on LAI. We conclude that the leaf area index of beech is mainly under control of age-related physiological factors, whereas the influence of soil chemistry and rainfall is comparably low.  相似文献   

10.
In coastal and highland Peru, totora,Schoenoplectus californicus (C. A. Meyer) Soják (Cyperaceae), has played a central cultural role. Totora was used to build boats, houses, bridges, mats, containers, clothing, string, and fans and has been noted for its use as both food (for humans and livestock) and fertilizer. We conducted unstructured interviews in Spanish and followed participant observation methods in Huanchaco and Lake Titicaca located in coastal and highland Peru, respectively. We hypothesized that a plant with high saliency to the local culture would have a high level of associated indigenous conservation practices. In addition, the level of care and management should increase as the resource became more valued or increasingly scarce. We found that, despite a long established tradition of sustainable use, the people were increasingly relying on intensive cultivation of this plant. The value of totora to local residents justified the efforts spent in maintaining adequate supplies of this plant. Increases in population, politics, and yearly variation in climate patterns have created a reduction in available totora and contributed to an increase in management practices.  相似文献   

11.
Abstract. For a 28-week period in late 1987 and early 1988, a study of seed-shedding by several heath species was carried out at the Muir of Dinnet in northeastern Scotland. The dominant species in the heath is Calluna vulgaris. Seed-shedding in Calluna began in early September 1987 and was completed in April 1988, with the period of maximum shedding falling between early November and late December 1987. The total numbers of seeds/m2 deposited in stands of Calluna in its four growth-phases were: pioneer, 18 910; building, 169010; mature, 198580; degenerate, 33900. Substantial loss of potential seeds results from the shedding of immature flowers. A control area close to, but outside the area of Calluna dominance had a deposition rate of 770 Calluna seeds/m2, indicating sufficient seed to colonise nearby available habitats. Seed rain was also recorded for several other heathland species: Erica cinerea, E. tetralix, Carex spp. and Betula pendula. Seeds of Erica cinerea were deposited in all the Calluna stands, 32670/m2 in the pioneer stand, 17600/m2 in building, 3720/m2 in mature, 210/m2 in degenerate (120/m2 in the control area). Numbers were greatest at the start of the sampling period, declining thereafter. This applied also to Betula seeds. Erica tetralix occurred in the degenerate Calluna stand and yielded 640 seeds/m2 (400/m2 in the control area). Seeds of Carex spp. were obtained in the control: 4110/m2. The method of sampling has a significant effect on the figures obtained. A method using tube collectors, emptied frequently, is recommended.  相似文献   

12.
Reliable and objective estimations of specific leaf area (SLA) and leaf area index (LAI) are essential for accurate estimates of the canopy carbon gain of trees. The variation in SLA with needle age and position in the crown was investigated for a 73-year-old Scots pine (Pinus sylvestris L.) stand in the Belgian Campine region. Allometric equations describing the projected needle area of the entire crown were developed, and used to estimate stand needle area. SLA (cm2 g−1) as significantly influenced by the position in the crown and by needle age (current-year versus 1-year-old needles). SLA increased significantly from the top to the bottom of the crown, and was significantly higher near the interior of the crown as compared to the crown edge. SLA of current-year needles was significantly higher than that of 1-year-old needles. Allometric relationships of projected needle area with different tree characteristics showed that stem diameter at breast height (DBH), tree height and crown depth were reliable predictors of projected needle area at the tree level. The allometric relationships between DBH and projected needle area at the tree level were used to predict stand-level needle area and estimate LAI. The LAI was 1.06 (m2 m−2) for current-year needles and 0.47 for 1-year-old needles, yielding a total stand LAI of 1.53.  相似文献   

13.
Abstract

The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root systems. We compared the seasonal pattern of live and dead fine-root mass (d < 2 mm), production and turnover in three beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree density reduced the total fine-root biomass (Coppice stand, 353.8 g m?2; Conversion 1994 stand, 203.6 g m?2; Conversion 2004 stand, 176.2 g m?2) which continued to be characterised by a bimodal pattern with two major peaks, one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand (production 131.5 g m?2 year?1; turnover rate 0.41 year?1) than in the converted stands (1994 Conversion stand: production 232 g m?2 year?1, turnover rate 1.06 year?1; 2004 Conversion stand: production 164.2 g m?2 year?1, turnover rate 0.79 year?1).  相似文献   

14.
In tropical mountains, trees are the dominant life form from sea level to above 4,000-m altitude under highly variable thermal conditions (range of mean annual temperatures: <8 to >28°C). How light-saturated net photosynthesis of tropical trees adapts to variation in temperature, atmospheric CO2 concentration, and further environmental factors, that change along elevation gradients, is not precisely known. With gas exchange measurements in mature trees, we determined light-saturated net photosynthesis at ambient temperature (T) and [CO2] (A sat) of 40 tree species from 21 families in tropical mountain forests at 1000-, 2000-, and 3000-m elevation in southern Ecuador. We tested the hypothesis that stand-level averages of A sat and leaf dark respiration (R D) per leaf area remain constant with elevation. Stand-level means of A sat were 8.8, 11.3, and 7.2?μmol?CO2?m?2?s?1; those of R D 0.8, 0.6, and 0.7?μmol?CO2?m?2?s?1 at 1000-, 2000-, and 3000-m elevation, respectively, with no significant altitudinal trend. We obtained coefficients of among-species variation in A sat and R D of 20–53% (n?=?10–16 tree species per stand). Examining our data in the context of a pan-tropical A sat data base for mature tropical trees (c. 170 species from 18 sites at variable elevation) revealed that area-based A sat decreases in tropical mountains by, on average, 1.3?μmol?CO2?m?2?s?1?per?km altitude increase (or by 0.2?μmol?CO2?m?2?s?1 per K temperature decrease). The A sat decrease occurred despite an increase in leaf mass per area with altitude. Local geological and soil fertility conditions and related foliar N and P concentrations considerably influenced the altitudinal A sat patterns. We conclude that elevation is an important influencing factor of the photosynthetic activity of tropical trees. Lowered A sat together with a reduced stand leaf area decrease canopy C gain with elevation in tropical mountains.  相似文献   

15.
Plant biomass, net primary productivity and dry matter turnover were studied in a grassland situated in a tropical monsoonal climate at Kurukshetra, India (29°58′N, 76°51′E). Based on differences in vegetation in response to microrelief, three stands were distinguished on the study site. The stand I was dominated by Sesbania bispinosa, stand II represented mixed grasses and stand III was dominated by Desmostachya bipinnata. Floristic composition of the three stands revealed the greatest number of species on stand II (75). The study of life form classes indicated a thero-cryptophytic flora. The biomass of live shoots in all the three stands attained a maximum value in September (424–1921 g m-2) and below ground plant biomass in November (749–1868 g m-2). The annual above ground net primary production was greatest on stand I (2143 g m-2) and lowest on stand II (617 g m-2). The rate of production was highest during the rainy season (15.34 to 3.18 g m-2 day-2). Below ground net production ranged from 1592 to 785 g m-2 y-2 and the rates were high in winter and summer seasons. Total annual net primary production was estimated to be 3141, 1403, 2493 and 2134 g m-2 on stands I, II, III and on the grassland as a whole, respectively. The turnover of total plant biomass plus below ground biomass indicated almost a complete replacement of phytomass within the year. The system transfer functions showed greater transfer of material from total net primary production to the shoot compartment during rainy season and to the root compartment during winter and summer seasons.  相似文献   

16.
Photosynthesis of marine benthic diatom mats was examined before and after sea ice breakout at a coastal site in eastern Antarctica (Casey). Before ice breakout the maximum under‐ice irradiance was between 2.5 and 8.2 μmol photons·m?2·s?1 and the benthic microalgal community was characterized by low Ek (12.1–32.3 μmol photons·m?2·s?1), low relETRmax (9.2–32.9), and high alpha (0.69–1.1). After breakout, 20 days later, the maximum irradiance had increased to between 293 and 840 μmol photons·m?2·s?1, Ek had increased by more than an order of magnitude (to 301–395 μmol photons·m?2·s?1), relETRmax had increased by more than five times (to 104–251), and alpha decreased by approximately 50% (to 0.42–0.68). During the same time interval the species composition of the mats changed, with a decline in the abundance of Trachyneis aspera (Karsten) Hustedt, Gyrosigma subsalsum Van Heurck, and Thalassiosira gracilis (Karsten) Hustedt and an increase in the abundance of Navicula glaciei Van Heurck. The benthic microalgal mats at Casey showed that species composition and photophysiology changed in response to the sudden natural increase in irradiance. This occurred through both succession shifts in the species composition of the mats and also an ability of individual cells to photoacclimate to the higher irradiances.  相似文献   

17.
A species of Zygogonium forms extensive dark purple mats in Yellowstone National Park in acidic habitats adjacent to thermal areas. These mats range up to 6 cm in thickness and up to 3000 m2 in areal extent. Temperatures in the mats varied from 20–31 C and pH varied from 2.4–3.1. These mats form on soil in areas where a moist surface is created by the presence of small acidic springs or seeps. The effect of light, temperature, and pH on photosynthesis was studied in the field by use of 14CO2. Photosynthesis increased in rate up to full sunlight; light inhibition was not observed. Temperature optimum for photo-synthesis was 25 C. A broad pH optimum was found between 1.0 and 5.0. The Zygogonium mats have a high water holding capacity and create a moist habitat in which Euglena and Chlamydomonas develop. The mats also serve as repositories for the eggs of the brine fly Ephydra bruesi and both larvae and adults of this fly probably consume Zygogonium filaments as their main food source.  相似文献   

18.
提升森林质量、修复生态功能是东北阔叶红松林生态修复的核心,而阐明林木与林分生长对采伐干扰的响应机理是其中的关键。森林对采伐干扰的响应会受到空间尺度、时间尺度以及干扰程度等因素的综合影响。以往的研究侧重于比较不同采伐处理下林木生长的相对大小,而忽视了不同恢复时间下,林木和林分生长随干扰程度的变化。以吉林蛟河阔叶红松林采伐样地为对象,基于连续四次样地调查数据(2011、2013、2015、2018年),分别探讨了林木和林分生长在不同恢复阶段对不同程度采伐干扰的响应,并通过构建分段模型确定采伐干扰阈值。结果显示:林木和林分生长对采伐干扰的响应并不一致,采伐促进了林木生长,并且林木生长量随采伐强度的升高而升高;采伐降低了林分生产力,林分生产力随采伐强度的升高而降低。林木和林分生长对采伐干扰的响应存在时滞效应:林木和林分生长在采伐后两年内并无显著变化,而在采伐三年后才发生明显变化。此外,分段模型的结果显示:当保留木断面积为21.6 m2/hm2时,林分生产力最高,表明通过密度调整使阔叶红松林胸高断面积维持在21.6 m2/hm2附近,可使林分处于较高的生产力水平、促进森林恢复。研究结果能够为制定科学的阔叶红松林生态修复策略提供技术支撑。  相似文献   

19.
Namsaraev  Z. B.  Gorlenko  V. M.  Namsaraev  B. B.  Buryukhaev  S. P.  Yurkov  V. V. 《Microbiology》2003,72(2):193-203
Microbial communities growing in the bed of the alkaline, sulfide hot spring Bol'sherechenskii (the Baikal rift area) were studied over many years (1986–2001). The effluent water temperature ranged from 72 to 74°C, pH was from 9.25 to 9.8, and sulfide content was from 12 to 13.4 mg/ml. Simultaneous effects of several extreme factors restrict the spread of phototrophic microorganisms. Visible microbial mat appears with a decrease in the temperature to 62°C and in sulfide content to 5.9 mg/l. Cyanobacteria predominated in all biological zones of the microbial mat. The filamentous cyanobacteria of the genus Phormidium are the major mat-forming organisms, whereas unicellular cyanobacteria and the filamentous green bacterium Chloroflexus aurantiacus are minor components of the phototrophic communities. No cyanobacteria of the species Mastigocladus laminosus, typical of neutral and subacid springs, were identified. Seventeen species of both anoxygenic phototrophic bacteria and cyanobacteria were isolated from the microbial mats, most of which exhibited optimum growth at 20 to 45°C. The anoxygenic phototrophs were neutrophiles with pH optimum at about 7. The cyanobacteria were the most adapted to the alkaline conditions in the spring. Their optimum growth was observed at pH 8.5–9.0. As determined by the in situ radioisotope method, the optimal growth and decomposition rates were observed at 40–32°C, which is 10–15°C lower than the same parameter in the sulfide-deficient Octopus Spring (Yellowstone, United States). The maximum chlorophyll a concentration was 555 mg/m2 at 40°C. The total rate of photosynthesis in the mats reached 1.3 g C/m2 per day. The maximum rate of dark fixation of carbon dioxide in the microbial mats was 0.806 g C/m2 per day. The maximum rate of sulfate reduction comprised 0.367 g S/m2 per day at 40°C. The rate of methanogenesis did not exceed 1.188 g C/m2 per day. The role of methanogenesis in the terminal decomposition of the organic matter was insignificant. Methane formation consumed 100 times less organic matter than sulfate reduction.  相似文献   

20.
To be able to estimate the cumulative carbon budget at broader scales, it is essential to understand net ecosystem exchanges (NEE) of carbon and water in various ages and types of ecosystems. Using eddy-covariance (EC) in Douglas-fir dominated forests in the Wind River Valley, Washington, USA, we measured NEE of carbon, water, and energy from July through September in a 40-year-old stand (40YR) in 1998, a 20-year-old stand (20YR) in 1999, and a 450-year-old stand (450YR) during both years. All three stands were net carbon sinks during the dry, warm summers, with mean net daily accumulation of –0.30 g C m–2 d–1, –2.76 g C m–2 d–1, and –0.38 g C m–2 d–1, respectively, in the 20YR, 40YR, and 450YR (average of 1998, 1999) stands; but for individual years, the 450YR stand was a carbon source in 1998 (0.51 g C m–2 d–1) and a sink in 1999 (–1.26 g C m–2 d–1). The interannual differences for the summer months were apparent for cumulative carbon exchange at the 450YR stand, which had 46.9 g C m–2 loss in 1998 and 115.9 g C m–2 gain in 1999. As predicted, the 40YR stand assimilated the most carbon and lost the least amount of water to the atmosphere through evapotranspiration.  相似文献   

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