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1.
Tree growth, survival and crop yield under agrisilvicultural practices were analyzed over a seven-year period in a split plot experiment on acid alfisol under rainfed conditions at ICAR Research Farm, Barapani (Meghalya), India. Three indigenous species including a fruit plant, and one introduced tree species formed the main plot treatments and three crop sequences were the sub-plot. The tree species were mandarin (Citrus reticulata), alder (Alnus nepalensis), cherry (Prunus cerasoides) and albizia (Paraserianthes falcataria), and the crop sequences were (a) soybean (Glycine max)-linseed (Linum usitatissimum) for three years, then groundnut (Arachis hypogea)-mustard (Brassica campestris) for three years followed by soybean-linseed in the seventh year, (b) groundnut-mustard for three years, then soybean-linseed for three years and groundnut-mustard in the seventh year, and (c) sole trees (‘tree only‘). A positive effect of intercropping on height and diameter growth, crown width and timber volume was observed in alder, albizia and cherry but no appreciable differences for these parameters were observed in mandarin between the two situations. Alder and albizia attained maximum growth and woody biomass followed by cherry and the minimum growth was recorded by mandarin. The better growth and timber volume in the ‘tree+crop’ situation was mainly due to the application of fertilizers and weeding. Crop yield reduction was observed with alder, mandarin and cherry and as the distance from tree increased, yield also improved. However, in albizia the proximity of tree did not reduce crop yield. The implications of the results are discussed in the context of the suitability of the species in this region and their usefulness in agroforestry systems. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

2.
Growth rate, resource partitioning, and several biological traits related to biological N2 fixation for six native or non-native tree species were compared using 15N isotope dilution techniques. The trees were field grown for six years in a semiarid mediterranean-climate region with five to six months a year of absolute drought. Trees were tested as candidates for new agroforestry systems being developed in central Chile to improve soil fertility and land health, while also increasing productivity and profitability for landowners and animal breeders. Four nitrogen-fixing legume trees (NFTs) were tested: Acacia caven (Mol.) Mol.Prosopis alba Griseb., P. chilensis (Mol.) Steuntz. emend. Burk., and Tagasaste ( Chamaecytisus proliferus L.f. subsp. palmensis (Christ.)Kunkel). Additional, non-nitrogen-fixing trees were the slow-growing native Huingán (Schinus polygamus (Cav.) Caberera and the fast-growing European Ash (Fraxinus excelsior L.). Among the NFTs, highly contrasting patterns in biological nitrogen fixation (BNF) were detected, for Ndfa (proportion of N derived from atmosphere), nodule efficiency (NE = gN fixed g–1 nodules), and N content in leaves, stems and roots. Tagasaste produced 2.5–25 times more biomass and fixed 4.5 to 30 times more atmospheric nitrogen than the South American Acacia and Prosopis species. Ndfa reached 250 g plant–1 in Tagastaste, in the sixth year, with NE = maximum 2.68 in the 4th year, and 1.12 in the 6th year. In contrast, Acacia caven had by far the highest NE of the four NFTs – 12.13 in the 4th year and 6.6 in the 6th year. Whereas BNF in Tagasaste peaked in the fourth year, and declined thereafter, BNF in Acacia caven increased steadily over six years. Fraxinus excelsiorand Schinus polygamus had growth rates and biomass accumulation intermediate between that of Tagasaste and the South American NFTs.Results are discussed in relation to agroforestry, restoration of soil fertility, and ecological and economic rehabilitation of damaged ecosystems and landscapes.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

3.
A field experiment was conducted for eight cropping seasons from 1988 to 1991 in semiarid Machakos, Kenya, to compare the productivity of shrubs and crops in intercropping (alleycropping) versus block (sole) planting systems. The study, conducted in a split-plot experiment with three replications, consisted of two tree species (Leucaena leucocephala andSenna siamea syn.Cassia siamea) in the main-plots and combinations of two planting systems (alleycropping and block planting of the shrubs and maize) with five different ratios of land allocation for the shrub and crop (1000, 1585, 2080, 2575, and 0100) in sub-plots. Thus, a sole maize and a sole tree were included in the subplot treatments. The spacing between hedgerows of shrubs in intercropping was 6.7, 5, and 4 m, respectively, corresponding to 15, 20, and 25% land allocation to shrubs. The trees were pruned to 0.5 m height four times a year. Intercropped hedgerows of senna and leucaena produced 10% and 24% more biomass than their respective block planting systems. On average, leucaena produced more biomass than senna. Maize alleycropped with leucaena yielded 16% less grain than sole-crop maize, whereas senna intercropping caused hardly any maize-yield reduction. Compared with the respective sole-crop systems, leucaena intercropping did not affect land equivalent ratio (LER), whereas LER increased by 28% with senna intercropping. The different tree:crop land occupancy ratios did not affect the production of either the component species or of the total system, except that LER declined with incrreased spacing between hedgerows. It is concluded that in semiarid highlands of Kenya, leucaena and crops should better be grown in sole blocks, not in alleycropping. In the case of slow-growing species such as senna, intercropping is worthwhile to consider only if the additional labour needed does not pose a serious problem for management, and the species has fodder value.  相似文献   

4.
An experiment was conducted in an 11-year-old black walnut (Juglans nigra L.), red oak (Quercus rubra L.), maize (Zea mays L.) alley cropping system in the midwestern USA to examine the extent of tree-crop competition for nitrogen and decomposition dynamics of tree leaves and fine roots. A below-ground polyethylene root barrier (1.2 m deep) isolated black walnut roots from maize alleys in half the number of plots providing two treatments viz. barrier and no barrier. The percentage of N derived from fertilizer (%NDF) and fertilizer use efficiency (%UFN) were determined using 15N enriched fertilizer. Further, maize grain and stover biomass, tree leaf biomass, tissue N concentration, and N content were quantified in both treatments. The barrier treatment resulted in a significantly greater grain (67.3% more) and stover (37.2% more) biomass than the no barrier treatment. The %NDF in both grain and stover was higher in the no barrier treatment as a result of competition from tree roots for water and mineralized N in soil. Maize plants growing in the no barrier treatment had a lower %UFN than those in the barrier treatment due to their smaller size and inability to take up fertilizer. Analysis of tree leaf and fine root decomposition patterns revealed faster release of N (39% over 15 days for black walnut and 17.7% for red oak) and P (30% over 15 days for both species) from roots compared to the leaves of both species. Following an early release of P (11.3% over 45 days), red oak leaves exhibited significant immobilization for the rest of the incubation period. The data indicate that competition for N from fertilizer is minimal since nutrient acquisition is not simultaneous among black walnut and maize. However, competition for mineralized N in soil can exist between black walnut and maize depending on water availability and competition. Tree leaves and fine roots can enhance soil nutrient pools through the addition of soil carbon and nutrients. Tree fine roots seem to play a more significant role in nutrient cycling within the alley cropping system because of their faster release of both N and P as compared to leaves. Selection of tree species and their phenology will impact the magnitude and rate of nutrient cycling.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

5.
Fine root dynamics of shaded cacao plantations in Costa Rica   总被引：1，自引：0，他引：1  
Root turnover may contribute a significant proportion of recycled nutrients in agroforestry systems and competition between trees and crops for nutrients and water may depend on temporal fine root regrowth patterns. Fine root biomass ( 2 mm) and fine root productivity were measured during one year in plantations of cacao (Theobroma cacao) shaded by Erythrina poeppigiana or Cordia alliodora planted on a deep alluvial soil in Turrialba, Costa Rica. Fine root biomass of approximately 1.0 Mg ha–1 varied little during the year with maximum values at the beginning of the rainy season of 1.85 Mg ha–1 in the cacao-C. alliodora system compared to 1.20 Mg ha–1 for cacao-E. poeppigiana. Fine root productivity of C. alliodora and E. poeppigiana (maximum of 205 and 120 kg ha–1 4 week–1, respectively) was greatest at the end of the rainy season, while for cacao it was greatest at the beginning of the rainy season (34–68 kg ha–1 4 week–1), which suggests that if nutrient competition occurs between the shade trees and the cacao, it could be minimized by early fertilization during the beginning of the rains immediately after pruning the shade trees. Annual fine root turnover was close to 1.0 in both systems. Assuming that fine root biomass in these mature plantations was constant on an annual basis, nutrient inputs from fine root turnover were estimated as 23–24 (N), 2 (P), 14–16 (K), 7–11 (Ca) and 3–10 (Mg) kg ha–1 year–1, representing 6–13% and 3–6% of total nutrient input in organic matter in the C. alliodora and E. poeppigiana systems, respectively.  相似文献   

6.
A study on dry matter production and nutrient cycling in agroforestry systems of mandarin grown in association with N2-fixing Albizia and mixed tree species (non-N2-fixing) was carried out in the Sikkim Himalaya. A site with Albizia was referred asAlbizia-mandarin stand and the other site with mixed tree species as mandarin stand. The stand total biomass, net primary productivity and mandarin fruit production was higher under the influence of Albizia. Agronomic yield of crops remained nearly the same in both the stands. Nitrogen and phosphorus concentrations of different components of Albizia were higher than those of mixed tree species, whereas their back translocation from leaf to branch before abscission was lower inAlbizia. The mandarin-based agroforestry is a highly nutrient-exhaustive system evaluated in terms of nutrient exit through the removal of agronomic yield. This system, under the influence of Albizia, was more productive with faster rates of nutrient cycling. Nutrient use efficiency increased under the influence of Albizia, in contrary to the hypothesis that efficiency should decrease with increasing rate of uptake. The poor nutrient conservation of Albizia, and malleability of nutrient cycling under its influence make it an excellent association which promotes higher availability and faster cycling of nutrients.Albizia should be utilised more extensively in the management of mandarin-based agroforestry systems.  相似文献   

7.
Litterfall and decomposition were studied in agroforestry systems involving large cardamom (Amomum subulatum) and mandarin (Citrus reticulata) in the Sikkim Himalaya, India. There were stands with N2-fixing trees (Alnus nepalensis over large cardamom, and Albizia stipulata over mandarin agroforestry) or without them (native non-symbiotic mixed tree species) in both systems. The total annual litter (litter + crop residue) production was higher in the Alnus-cardamom than in the forest-cardamom stand and in the mandarin than in the Albizia-mandarin stand. The ratio of litter production to floor litter was higher in the N2-fixing stands than in the non-N2-fixing stands, indicating a faster litter turnover in the former. Tree litterfall occurred throughout the year, but with marked peaks during November to April. Total soluble polyphenolics of fresh litter were higher in N2-fixing species than in mixed tree species and crops. Half-life values for ash-free mass were shortest in the leaves of N2-fixing species. N loss was higher from N2-fixing Alnus and Albizia leaves, whereas P loss was faster and nearly equal in Alnus leaf litter and cardamom residue in cardamom, and Albizia leaf litter and crop residue in mandarin agroforestry systems. The P turnover in N2-fixing Alnus and Albizia twigs was faster than in the twigs of mixed tree species. The N2-fixing tree species increased the N and P cycling through production of more above-ground litter and influenced greater release of these nutrients.  相似文献   

8.
Above ground oven dried biomass (BM) of individual trees in young stands of Acacia salicina Lindl. and Eucalyptus occidentalis Endl. were correlated linearly and logarithmically to the square of the basal diameter at 0.2 m (DB) and to the latter multiplied by the height of the tree. Number of main stems at basal height per tree were included as well. DB measurements in young Eucalypt stands provided better BM estimates than the commonly used diameter at breast height (1.3 m) (DBH).The following biometric relationships, after cross-validation against an independent data set, showed the best fit: BM=0.1282* (DB2) and BM=0.1700* (DB2) for A. salicina and E. occidentalis, respectively, with (DB2) ranging from 0–400 cm2 and BM in kg tree–1. For acceptable relative errors in biomass estimations (DB2) should be larger than 100 cm2.Foliage to wood ratios at (DB2)<100 cm2 for both tree species generally exceeded 1, but rapidly leveled off at 0.81±0.28 and 0.92±0.19 for the Acacia and Eucalypt spp., respectively, at higher (DB2) values.  相似文献   

9.
The biomass and the spatial distribution of fine and small roots were studied in two Japanese black pine (Pinus thunbergii Parl.) stands growing on a sandy soil. More biomass of fine and small roots was found in the 17-year-old than in the 40-year-old stand. There were 62 g m−2 of fine roots and 56 g m−2 of small roots in the older stand, which represented mean values of 608 g for fine and 552 g for small roots per tree, respectively. In the younger stand, a total of 85 g m−2 of fine roots and 66 g m−2 of small roots were determined, representing a mean of 238 g for fine and 186 g for small roots per tree, respectively. Fine and small root biomasses decreased linearly with a soil depth of 0–50 cm in the older stand. In the younger stand, the fine and small roots developed only up to a depth of 30 cm. Horizontal distributions (with regard to distance from a tree) of both root groups were homogeneous. A positive correlation in the amount of biomass of fine and small roots per m2 relative to tree size was found. Fine and small root biomasses increased consistently from April to July in both stands. The results also indicated earlier growth activity of the fine roots than small roots at the beginning of the growing season. The seasonal increases in fine and small root biomasses were slightly higher in the younger stand than the older stand.  相似文献   

10.
Litterfall, forest-floor litter biomass and nutrients, short-term litter decomposition and the effects of leaf mulches on initial growth of maize were studied for four indigenous tree species with agroforestry potential:Stryphnodendron microstachyum Poepp. et Endl.(S. excelsum), Vochysia ferruginea Mart,Vochysia guatemalensis Donn. Sm. (V. hondurensis) andHyeronima alchorneoides (O), growing in a young experimental plantation in the Atlantic humid lowlands of Costa Rica. Total annual leaf litterfall was higher inV. ferruginea plots, followed byS. microstachyum, V. guatemalensis andH. alchorneoides; all with values comparable to those reported for other tree species grown in agroforestry combinations in humid tropical regions. Forest-floor litter accumulation was highest underV. ferruginea andV. guatemalensis. Both litterfall and forest-floor litter material had similar patterns in nutrient concentrations: N was higher inS. microstachyum, Ca was higher inV. guatemalensis, K was higher inH. alchorneoides; Mg was higher inV. guatemalensis andH. alchorneoides; H. alchorneoides andV. guatemalensis had the highest P.V. ferruginea litter decomposed more slowly, whileS. microstachyum apparently decomposed faster than the other species. The twoVochysia species showed increases in N and P concentration in decomposing litter after seven weeks in the field,H. alchorneoides showed an increase in litter N and a decrease in litter P, andS. microstachyum showed a net decrease in both N and P over the same time period. The patterns found in the litter bag study were confirmed by results obtained in a tethered-leaves experiment.S. microstachyum andV. ferruginea litters lost more weight when mixed in a 11 proportion than either of them alone. Maize seedlings growing in plots mulched withS. microstachyum andH. alchorneoides leaves showed greatest initial growth, confirming patterns found in decomposition and nutrient release studies. The results show that these species could be used in agroforestry combinations with different advantages according to the specific objectives desired, whether these are soil protection, nutrient recycling, or enhancement of the growth of associated crops.  相似文献   

11.
On fertile alluvial soils on the lakeshore plain of Malawi, maize (Zea mays L.) yields beneath canopies of large Faidherbia albida (synAcacia albida) trees greatly exceed those found beyound tree canopies, yet there is little difference in soil nutrients or organic matter. To investigate the possibility that soil nutrient dynamics contribute to increased maize yields, this study focused on the impact of Faidherbia albida on nitrogen mineralization and soil moisture from the time of crop planting until harvest. Both large and small trees were studied to consider whether tree effects change as trees mature.During the first month of the rainy season, a seven-fold difference in net N mineralization was recorded beneath large tree canopies compared to rates measured in open sites. The initial pulse beneath the trees was 60 g N g–1 in the top 15 cm of soil. During the rest of the cropping cycle, N availability was 1.5 to 3 times higher beneath tree canopies than in open sites. The total production of N for the 4-month study period was 112 g N g–1 below tree canopies compared to 42 g N g–1 beyond the canopies. Soil moisture in the 0–15 cm soil layer was higher under the influence of the tree canopies. The canopy versus open site difference grew from 4% at the beginning of the season to 50% at the end of the cropping season.Both N mineralization and soil moisture were decreased below young trees. Hence, the impact of F. albida on these soil properties changes with tree age and size. While maize yields were not depressed beneath young F. albida, it is important to realize that the full benefits of this traditional agroforestry system may require decades to develop.  相似文献   

12.
The use of agroforestry systems in which pruning from trees is used to mulch the companion crops is an important area of research in the tropics. However, previous studies mostly evaluated the contribution of mulch to soil improvement and rarely examined the effect of mulch on weeds. Field experiments were conducted during the 1995 and 1996 growing seasons to investigate the effects of mulch from three woody fallow species on weed composition, biomass and maize grain yield. Treatments consisted of mulch from Leucaena leucocephala, Gliricidia sepium, and Senna siamea applied at rates of five and three tons dry matter ha–1 at planting and three weeks after planting (WAP), respectively, an unmulched treatment that received 90 kg N ha–1 of inorganic fertiliser, and an unmulched control plot that received no fertiliser. In both years and sampling dates, plots mulched with G. sepium and S. siamea had significantly lower weed density and biomass than the control plot in each of the sampling times and year of study. There was no significant difference in either weed density or biomass between the plot mulched with L. leucocephala and the unmulched plots. Mulches from G. sepium and S. siamea reduced weed density and weed biomass, while L. leucocephala was less effective in reducing weed biomass and weed density. Weed reduction by the mulches was in the order G. sepium S. siamea > L. leucocephala. Sedges were the dominant species in all the treatments except in G. sepium plots, where Talinum triangulare and other broadleaved species were dominant.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

13.
Growing concern for economic and environmental issues emphasizes the potential value of intercropping systems in temperate regions. However, the selection of relevant tree species to be associated with crops has been little documented. The growth and the nitrogen nutrition of two economically valuable species, wild cherry (Prunus avium L.) and hybrid walnut (Juglans nigra L.×Juglans regia L.), were compared over six years after plantation. These two species were associated with non-irrigated cereal crops in the agroforestry treatment or grown separately (weeded control and fallow). Intercropping increased diameter growth as soon as year 2 in the two species. Leaf biomass assessment using allometric models showed an earlier and greater leaf biomass increase in hybrid walnut than in wild cherry tree. After six years, the relative growth increase of the agroforestry trees with respect to the control trees varied with the parameter considered (diameter at breast height from +26 to +65%, leaf biomass from +54 to +142%) and with the tree species (higher relative growth for hybrid walnut trees). The beneficial effect on tree growth can be accounted for in terms of enhanced nitrogen nutrition. The tree–crop association in intercropping systems, which improves tree growth, might thus allow the planting of more demanding trees on soils of lower fertility.  相似文献   

14.
In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water.  相似文献   

15.
The decomposition of leaves, twigs and roots of two diameter classes (<1.5 mm, 1.5–5 mm) were examined in an alley cropping experiment withGliricidia sepium, Calliandra calothyrsus andSenna sianea in the subhumid savanna of Central Togo using the litterbag technique. The effect of the application of leaves and twigs as mulch or green manure was examined. Gliricidia showed the most rapid mass loss. For all species, leaves decomposed faster than roots. Twigs had the lowest decomposition rate except forCalliandra. The two diameter classes of roots decomposed differently in the three species:Gliricidia fine roots decomposed faster than its coarser root fraction, the coarse roots ofSenna decomposed faster than the fine roots.Termites influenced the mass loss of twigs and roots to varying extents for the different species. In the case of twigs this was markedly influenced by the mode of application: green manure showed more termite frass than mulch.Nutrient release resembled the mass loss patterns of the prunings except for K, which was leached independently from mass loss. The release of the different nutrients was in the order CaGliricidia andSenna seemed to be best for mulch and green manure production at our site.  相似文献   

16.
To assess the possible degree of root competition from fruit trees which could potentially be used in agroforestry systems, fine root density of fruit trees Strychnos cocculoides Bak., Strychnos spinosa Lam. (Loganiaceae) and Vangueria infausta Burch. (Rubiaceae), as well as from the shrubby species, Grewia flava DC. (Tiliaceae) was investigated. Vangueria infausta had the highest fine root densities in both vertical and horizontal extensions. In Vangueria infausta fine root density decreased with increasing soil depth. For the other species in the 80 cm soil profile investigated, no significant changes in fine root density with soil depth were found. For Strychnos cocculoides almost no fine roots were detected in the upper soil horizon (0–20 cm). Using fine root surface area densities, exploration and exploitation indices were calculated. Vangueria infausta had the highest value of the exploration index compared to the other species. For use in agroforestry systems Vangueria infausta was estimated to be the most competitive of the investigated species, whereas Strychnos cocculoides seems to be the less competitive. Strychnos cocculoides has additionally spatial arrangements of fine roots favourable for agroforestry, slowly increasing with depth and additionally low concentrations in upper soil layers.  相似文献   

17.
The effect of tree species on the characteristics of the herbaceous stratum, during the first five years of a fallow, was evaluated in the North of Cameroon (average annual temperature 28.2 °C, total annual rainfall 1050 mm). Treatments included a natural grazed herbaceous fallow, a natural ungrazed herbaceous fallow and three planted tree fallows (Acacia polyacantha Willd. ssp. campylacantha (Hochst. ex A. Rich.), Senna siamea Lam. and Eucalyptus camaldulensis Dehnh.), which were protected against grazing. Because tree species influenced light interception in different ways, as well as having different root patterns, they had different effects on the herbaceous stratum in terms of species composition and biomass. The grazed herbaceous fallow maintained the greatest species richness. Protection against grazing or the introduction of tree species associated with the absence of grazing induced both a progressive evolution to a particular species composition. The ungrazed herbaceous fallow consisted mainly of Andropogon gayanus Kunth, which provided the greatest biomass (8 t dry matter ha–1 at the end of the fallow period). E. camaldulensis provided little shade and the lowest fine root mass in the top layer allowing the growth of A. gayanus and thus a greater herbaceous biomass (3.5 t DM ha–1) than that found under the other tree species. Under the heavy shade of A. polyacantha, the herbaceous stratum consisted mainly of annual Pennisetum spp. (2.2 t DM ha–1) and showed the greatest N concentration (1.3%), probably due to N2 fixation by the tree species. After the fourth year, despite the relatively open tree canopy, S. siamea, which showed the highest fine root mass, had a strong depressive effect on the herbaceous stratum. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

18.
Energy efficiency of agroforestry systems of large cardamom grown under N2-fixing Himalayan alder (alder-cardamom) and natural forest (forest-cardamom) was studied in the Sikkim Himalaya. Large cardamom (Amomum subulatum), the most important perennial cash crop of the region, is widely cultivated with Himalayan alder (Alnus nepalensis) as shade tree. Energy fixation, storage, net allocation in agronomic yield, and heat release and exit from the system were respectively 1.57, 1.44, 2.24 and 2.22 times higher in the alder-cardamom compared to the forest-cardamom system. Energy conversion efficiency and net ecosystem energy increment were also higher in the alder-cardamom than the forest-cardamom system. Energy fixation efficiency and energy conversion efficiency of large cardamom increased under the influence of Himalayan alder. Energy efficiency in N2-fixation of Himalayan alder was also high (67.5 g N2 fixed 104 kJ-1 energy). Quantum and flux of energy increased in the alder-cardamom compared to the forest-cardamom system that optimized the production potential of the cash crop under the influence of the Himalayan alder. Climatic sympatry of the large cardamom and Himalayan alder, and their synergetic energy efficiency makes this association ecologically and economically viable for the mountain regions.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

19.
In vitro cultures were initiated from shoots taken from seedlings ofFaidherbia albida on Murashige and Skoog based medium supplemented with different combinations of 6-benzylaminopurine (BA) and -naphthaleneacetic acid (NAA). The shoots grew and rooted on all media. Rooting and vigorous growth were most successful on medium supplemented with 10–7M NAA alone on which 87% of the shoots formed roots. Seventy-one percent of plantlets which were transferred to soil were successfully established and nodulated with the nativeRhizobium. The procedures provide a basis for the development of in vitro techniques for rapid multiplication and physiological studies of the species.  相似文献   

20.
We measured photosynthetically active radiation (PAR) beneath the forest canopy, understory species richness and diversity, and biomass in a Larix leptolepis plantation in central Korea 4 years after thinning. Four different thinning intensities (control, 10%, 20%, and 40% stocking reduction) were applied in 1997. Mean annual intercepted PAR at 30cm and 1m above ground level was significantly different among the thinning intensities and strongly correlated with the number of stems remaining after thinning. Understory species richness and diversity were lowest in the unthinned stands and increased with thinning intensity, and there were significant correlations between the total number of understory species or diversity index (Shannons diversity index, H) and the number of stems per hectare after thinning. Also understory above-ground biomass was significantly increased with thinning intensity in both sampling months (June and August 2001). Thinning increased light inputs to the ground and resulted in higher species richness and diversity and above-ground biomass. These results suggested that light availability and understory responses to thinning at a comparable intensity are likely to last well beyond the 4 years of this study.  相似文献   

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