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51.
Near a hen house (50–600 m), vitality ofPinus sylvestris, N-, P-, K-, Ca-, Mg-contents of the needles, N-, Mg-, K-, Ca- and Al-contents in soil extracts and NH3/NH
4
+
-contents of the air were determined. Damage symptoms occurred when N-immissions hit the canopy directly. In contrast no visible decline of the above ground plant could be observed if N was mainly deposited on the soil. 相似文献
52.
The pH of weak-acid solutions is controlled by acid concentration (HA + A–), the degree of acid dissociation (A–/HA), and the strength of the acids present (pKa). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmolc/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmolc/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmolc/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use). 相似文献
53.
Classification and ordination of macroinvertebrate assemblages to predict stream acidity in upland Wales 总被引:2,自引:2,他引:0
Macroinvertebrates were collected from riffles at 104 sites in upland Wales during April and July 1984. Species assemblages were ordinated by DECORANA, classified by TWINSPAN and related to stream chemistry and other environmental factors using correlation and multiple discriminant analysis. DECORANA axis 1 was most strongly correlated with pH and aluminium concentration whilst axis 2 correlated with stream gradient and flow. Four TWINSPAN site groups established in each season were also principally related to pH and aluminium concentration, and reflected overall taxon-richness; differences between groups were most apparent during spring, when catchment forest cover and taxon-richness were also related. A dichotomous key based on indicator species was established for each season with the coleopteran Hydraena gracilis Germar and the Ephemeroptera, including Baetis rhodani Pictet, important indicators at Level 1. We propose that these indicator systems may be used for the rapid detection and assessment of acid waters throughout Wales, and that the methodology is applicable generally. 相似文献
54.
Vegetation dynamics in the coastal area of the Seto Inland Sea region in Japan, where wild fires occur frequently, were described
using a stationary Markov model. In this region, vegetation types ofMiscanthus-Pleioblastus grassland,Lespedeza-Mallotus scrub,Pinus-Rhododendron forest andCrassocephalum-Erechtites community have been identified, and these show cyclic succession under the influence of fires.
The model uses parameters determining fire frequency and rate of successional change to analyze the effect of variation in
these parameters on the areal ratio of each vegetation type at equilibrium and on the time taken for one vegetation type to
succeed another (elapsed successional time). The effect of fire frequency differs between hypothetical habitats with high
and low productivity. A policy for vegetation management in areas of high and low productivity is proposed. The advantages
and limitations of applying Markov models to studies of vegetation succession are also discussed. 相似文献
55.
Eizi Suzuki 《Journal of plant research》1990,103(3):297-312
In two forest stands, one domonated byAbies spectabilis, and the other byPinus wallichiana-Picea smithiana, 198 cores were taken from 105 conifers in May 1983 and the annual ring widths were measured. The annual ring widths usually
had significant similarities between cores taken from the same tree and with cores taken from different trees. these similarities
increased with tree size. The climatic change affected the large trees more strongly than it did the small trees. Micro environmental
changes, such as canopy gap affected the small trees more strongly. Annual ring widths were also correlated with the annual
precipitations at Jumla 30 km south of the plots for a recent 20 year period. A multiple regression analysis between ring
width and seasonal precipitation showed that the growth ofA. spectabilis was correlated primarily with the rain from May to August and secondarily with that from September to December in the previous
year. 相似文献
56.
Data are presented from a 16-month study of proboscis monkeys in an area of mixed coastal forest in Sarawak. The population
density, social organization, and feeding and ranging behavior are described in detail. Results are compared with those from
other primates in an attempt to understand why females of certain species (including proboscis monkeys) transfer between social
groups. The scarcity of available food and reasons for the limited habitat preferences of proboscis monkeys are also discussed. 相似文献
57.
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
58.
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
59.
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
60.
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