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71.
72.
Takashi Kohyama 《Journal of plant research》1988,101(2):207-212
A simple relation (v-lnB) (u-lnx)=c was recognized betweenx as dbh (or individual basal area) andB as the cumulative basal area abovex, for various stands of warm-temperate rain forests of Yakushima Island, southern Japan (v, u andc, parameters). The model parameters explained a difference in the pattern of stand development between secondary succession
after clear-felling and gap regeneration within primary forests. 相似文献
73.
若干铁杉属植物核型的比较研究 总被引:5,自引:0,他引:5
本文首次报道了我国特产的重点保护植物南方铁杉的核型,全由中部和近中部着丝点染色体构成,核型公式为K(2n)=2x=24=20m+4sm,属“ 2A”类型。染色体的相对长度组成为2n=24=12M_2+10M_1+2S。通过比较。发现东亚的南方铁杉的核型与台湾铁杉甚为相似而略具进化的趋势,但北美东部的卡罗来纳铁杉的核型比它们进化得多。本文支持Florin认为铁杉属至少在早第三纪存在一条从欧亚大陆经过白令海峡到达北美洲的迁移路线的意见。 相似文献
74.
本文应用开口托盘式集水器收集不同土层的渗透水,研究尖峰岭热带山地雨林,半落叶季雨林及其游耕地的土壤渗透水状况,分析了不同植被—土壤类型与利用状况的渗透特点、降水与渗透水的关系、渗透水量与水质的动态变化,初步揭示了尖峰岭热带林对水分的输导—涵贮性能,及热带林生态系统中物质迁移的特点,并据此分析了游耕农业的生态恶果。 相似文献
75.
Physiognomy, structure and floristic composition of one hectare of lowland tropical rain forest was studied in detail at Los Tuxtlas, Mexico. Physiognomically, the Los Tuxtlas forest should be classified as lowland tropical high evergreen rain forest. The forest showed a closed canopy at 30–35 m. Of all woody, non-climbing species with a DBH1.0 cm 89.4% (94.5% of all individuals) were evergreen, 25.4% (59.5% of the individuals) had compound leaves, and over 80% of species (and individuals) had leaves in the notophyll and mesophyll size classes. The forest structure was characterized by a low density (2976 individuals with a DBH1.0 cm, 346 individuals with a DBH10.0 cm, per ha, excluding vines) with an average basal area (38.1 m2, DBH1.0 cm, 34.9 m2, DBH10.0 cm, per ha, excluding vines). This was attributed to the relative maturity of the forest on the study plot. The study plot contained 234 species (11 208 individuals with a height 0.5 m), of which 55.1% (34.8% of individuals) were trees, 9.4% (6.8%) shrubs, 3.4% (44.3%) palms, 20.1% (5.2%) vines, 6.8% (8.7%) herbs and 5.1% (0.3%) of unknown lifeform. Furthermore, 58 species of epiphytes and hemi-epiphytes were found. Diversity of trees, shrubs and palms with a DBH1.0 cm was calculated as Shannon-Wiener index (4.65), Equitability index (0.65), and Simpson index (0.10). The dominance-diversity curve showed a lognormal form, characteristic for tropical rain forest. The community structure was characterized by a relative dominance of Astrocaryum mexicanum in the understorey, Pseudolmedia oxyphyllaria in the middle storeys, and Nectandra ambigens in the canopy. Species population structures of 31 species showed three characteristic patterns, differentiated by recruitment: continuously high, discontinuously high, and continuously low recruitment. Height/diameter and crown cover/diameter diagrams suggested a very gradual shift from height growth to crown growth during tree development. Forest turnover was calculated as 138 years. Compared to other tropical rain forests the Los Tuxtlas forest had 1. similar leaf physiognomical characteristics, 2. a lower diversity, 3. a lower density, 4. an average basal area, and 5. a slow canopy turnover. 相似文献
76.
Tree replacement patterns in subalpine Abies-Betula forests,Wolong Natural Reserve,China 总被引:1,自引:0,他引:1
Vegetation in canopy gaps of two old-growth Abies-Betula forest stands, one with bamboo the other without, was measured. The structure of gap vegetation at each site was used to derive tree replacement probabilities. Transition probabilities indicate different tree replacement trends in forests with bamboo compared to those without. Projected compositions show Betula to be the most abundant species in bamboo stands while Abies remains most abundant where bamboo was absent. A dense bamboo sward seems to reduce the probability of Abies filling gaps by inhibiting establishment and growth of seedlings. Bamboo preempts space after canopy gap formation by increasing shoot production which reduces opportunities for establishment and growth of other woody species. Differences in dispersal ability and longevity of Abies and Betula appear to be important factors contributing to their coexistence forests with a small canopy gap disturbance regime. 相似文献
78.
Takuji Hoshino 《Journal of plant research》1992,105(4):639-648
Chromosome numbers were determined for 342 clones ofCarex oxyandra collected from 35 localities in Hokkaido, Honshu, Shikoku and Kyushu, Japan. Four intraspecific aneuploids, 2n=18, 20, 24 and 26, were found. In meiotic division, only bivalent chromosomes were observed in all clones at metaphases I
and II, suggesting that the aneuploids are established gamodemes. In the mitotic metaphase chromosomes, trimodal variation
in chromosome length was observed. The 2n=26 clones found on Mt. Hiko had two particularly small chromosomes. The cytodemes with higher number of chromosomes are distributed
in more southern areas of Japan.Carex oxyandra, therefore, accompanied with chromosome fragmentations, might spread the geographical distribution to the southern parts.
The morphological characters of leaves, spikes, scales, perigynia and nuts were similar among the four cytodemes, except for
the small leaves on plants from Yaku Island. 相似文献
79.
Arndt Brüning 《Oecologia》1991,86(4):478-483
Summary The predation on spiders in a forest ecosystem by a colony of red wood ants, Formica polyctena, was estimated using a barrier to isolate the colony. Of the ants' total prey, 4.6% were spiders. In order to estimate the effect of F. polyctena within their hunting area on the spider population, the spiders' population density was studied inside and outside the hunting area. Samples of the forest floor were taken, spider webs were counted and pitfall traps were used. No significant difference was found in density or composition of the spider fauna inside and outside the hunting area. 相似文献
80.
A. J. M. Stams H. W. G. Booltink I. J. Lutke-Schipholt B. Beemsterboer J. R. W. Woittiez N. van Breemen 《Biogeochemistry》1991,13(3):241-255
To demonstrate the contribution of atmospheric ammonium to soil acidification in acid forest soils, a field study with13N-ammonium as tracer was performed in an oak-birch forest soil. Monitoring and analysis of soil solutions from various depths on the13N-ammonium and15N-nitrate contents, showed that about 54% of the applied15N-ammonium was oxidized to nitrate in the forest floor. Over a period of one year about 20% of the15N remained as organic nitrogen in this layer. The percentage15N enrichment in ammonium and nitrate were in the same range in all the forest floor percolates, indicating that even in extremely acid forest soils (pH < 4) nitrate formation from ammonium can occur. Clearly, atmospheric ammonium can contribute to soil acidification even at low soil pH. 相似文献