Tree diversity in sacred groves of the Jaintia hills in Meghalaya, northeast India

Biodiversity of woody species was investigated in Ialong and Raliangsacred groves of the Jaintia hills in Meghalaya, northeast India. These grovesrepresent the climax subtropical broad-leaved forest of the area. A total of 738individuals belonging to 82 species, 59 genera and 39 families was identified ina 0.5 ha plot of the Ialong sacred grove, whereas the same area in theRaliang sacred grove had 469 individuals of 80 species, 62 genera and 41families. About 32% species were common to both groves. Lauraceae, with10–17 species, was the dominant family. The canopy and subcanopy stratawere respectively composed of 28 and 33% of the total tree species in theforest. The number of species as well as stem density were greater for the treesof lower dbh (5–15 cm) class compared to the higher (> 66cm) dbh class. The majority of the species showed a contagiousdistribution pattern and low frequency. The basal area varied from 57.4 to 71.4m² ha^–1. Species richness within theforest varied from 3 to 15 per 100 m² in Ialong and 3 to 12 per 100m² in Raliang. The dominance–distribution curves showed highequitability and low dominance in both groves.     

Diversity and structural patterns for tropical montane and premontane forests of central Peru,with an assessment of the use of higher-taxon surrogacy

The Chanchamayo valley in the Peruvian Andes formerly contained large areas of montane and premontane tropical forests, although logging and agricultural expansion has resulted in extensive deforestation and habitat fragmentation. This study evaluates the regional context of the valley by a comparison of data from a series of one hectare plots giving data on the diversity and structure of trees ≥10 dbh, and then examines in more detail data from a 1 ha plot located in a newly declared conservation area (Pampa Hermosa Reserved Zone) embodying one of the most intact forest remains. An explicit goal was also to test the efficacy of sampling using taxonomic surrogacy, which could provide an effective means of making more efficient such work among diverse tropical forests. The Cedros de Pampa Hermosa plot contained 444 individuals belonging to 135 species, 66 genera and 35 families. The families Lauraceae, Meliaceae, Moraceae and Urticaceae provided over half of the individuals counted. The high representation of Urticaceae species suggests a disturbance regime driven by the large sizes of the Meliaceae species and their dynamics on steep slopes. Indicator species analyses supported other evidence that this site at 1,600 m is located in a broad ecotonal area transitioning to premontane and lowland rain forests. Ordinations (nMDS) based on Bray–Curtis similarities and total abundance, basal areas and presence-absence data of the 598 species (3,469 individuals) found on all seven one hectare plots sampled in the valley showed a clear separation into three tree assemblage types, namely the lower montane site, and two others on the eastern and western sides of the valley. Ordination patterns were quite similar at species and family level, but did not show any site groupings at the generic level, suggesting important turnover of species and families along environmental gradients. A number of species could not be allocated to known taxonomic groups, and were evaluated as morphotaxa. The inclusion or exclusion of such taxa did not dramatically alter the main ordination patterns within taxonomic levels of botanical family or of species, which implies that rapid inventory methods and incomplete identifications can still provide data useful for conservation planning in this and similar forests.     

西双版纳热带山地雨林群落乔木树种多样性研究

根据块样地资料对西双版纳热带山地雨林树种多样性特征进行了分析.结果表明,在2 500m²的样地上,随着起测胸径递增,各样地乔木个体数和树种丰富度均表现为依次递减;低海拔带上(850～1000 m)的山地雨林(1、2号样地)的各指数值无一定变化规律,较高海拔带上(1200～2000 m)的山地雨林(3～6号样地)的Shannon-Wiener指数和Simpson指数均表现为依次递减,而Pielou均匀度指数则呈依次递增的趋势.较高海拔带上的山地雨林在较小乔木起测胸径(≥2 cm、≥5 cm、≥10 cm)的树种丰富度、多样性和均匀度指数均要明显大于低海拔带上的山地雨林,而两者在较大乔木起测胸径(≥20 cm、≥30 cm、≥50 cm)的各指数值无明显差异.随着取样面积的递增,各样地树种丰富度、多样性和均匀度指数在取样面积递增到2 000m²处均已趋于平缓.     

Effect of vesicular-arbuscular mycorrhizae on seedling growth of four tree species from the tropical deciduous forest in Mexico

The influence of vesicular-arbuscular mycorrhizae on the growth of seedlings of Caesalpinia eriostachys, Cordia alliodora, Ipomoea wolcottiana and Pithecellobium mangense was investigated in a greenhouse experiment conducted at the Biological Station of Chamela on the Pacific coast of Mexico. Dry biomass production, relative growth rate, root/shoot ratio and mycorrhizal dependency were quantified for 75-day-old seedlings. With the exception of the pioneer species I. wolcottiana, mycorrhizal infection resulted in increases in biomass production, relative growth rate and leaf area. The root/shoot ratios attained for the species, however, did not show a consistent trend with infection. Nevertheless, all species had root/shoot ratios below 1 with infection and only one, Cordia alliodora, had a ratio greater than 1 without infection. The two late successional species from the mature part of the forest, Caesalpinia eriostachys and P. mangense, showed a larger mycorrhizal dependency than the two associated with disturbed environments.     

Effects of flowering tree density on the mating system and gene flow in Shorea leprosula (Dipterocarpaceae) in Peninsular Malaysia

Pristine tropical rainforests in Southeast Asia have rich species diversity and are important habitats for many plant species. However, the extent of these forests has declined in recent decades and they have become fragmented due to human activities. These developments may reduce the genetic diversity of species within them and, consequently, the species’ ability to adapt to environmental changes. Our objective in the study presented here was to clarify the effect of tree density on the genetic diversity and gene flow patterns of Shorea leprosula Miq. populations in Peninsular Malaysia. For this purpose, we related genetic diversity and pollen flow parameters of seedling populations in study plots to the density of mature trees in their vicinity. The results show that gene diversity and allelic richness were not significantly correlated to the mature tree density. However, the number of rare alleles among the seedlings and the selfing rates of the mother trees were negatively correlated with the density of the adult trees. Furthermore, in a population with high mature tree density pollination distances were frequently <200 m, but in populations with low adult tree density the distances were longer. These findings suggest that the density of flowering trees affects selfing rates, gene flow and, thus, the genetic diversity of S. leprosula populations. We also found an individual S. leprosula tree with a unique reproductive system, probably apomictic, mating system.     

Tree form in a mixed dipterocarp forest in Indonesian Borneo

The form of tropical trees was studied with reference to the production structure of the component individuals of a tropical rain forest stand in Sebulu, East Kalimantan in Indonesian Borneo, since the production structure as a physical or bio-economical basis of tree form still remains obscure in tropical rain forests. The pipe model theory successfully explained the crown shapes of different trees, and its parameter, designated as specific pipe length, suggested an increase in the cost of leaf mass growth with an increase in crown size. A mathematical model consisting of exponential functions of aboveground height was applied for describing stem form, and its properties were examined through changes in its coefficients and by adopting an assumption of the geometrical similarity of individual stem form as a criterion for comparing differences in stem form among individual trees. Furthermore, the cost of buttersses was discussed using the relation between bole- and buttress weight calculated from the mathematical model.     

Short-term changes in tree populations in a tropical evergreen forest at Varagalaiar, Western Ghats, India

Within a 30-ha permanent plot of a tropical evergreen forest in the Anamalais, Indian Western Ghats, all the 13415 trees 30cmgbh (belonging to 153 species) were identified and tagged during 1997–1998. This communication reports the results of tree population changes based on two annual censuses (1999 and 2000) of the plot after the initial census, and compares the results with other tropical forest sites. One species, Ficus beddomei, disappeared from the plot and there was no new addition of species. Of the 96 species that showed changes in their population density, for 12 species recruitment and mortality matched. Tree recruitment (5 treesha^–1year^–1) exceeded mortality (4 treesha^–1year^–1) during the two-year period. Four modes of tree deaths were recorded in our site. The per cent mortality of trees differed between tree size classes during each recensus. The plot tree density increased progressively in the two-year period, indicating that shifts in species composition and density in natural forests, without major catastrophic disturbance, occur slowly.     

Intraspecific responses to climate in Pinus sylvestris

Abstract Five population-specific response functions were developed from quadratic models for 110 populations of Pinus sylvestris growing at 47 planting sites in Eurasia and North America. The functions predict 13 year height from climate: degree-days > 5 °C; mean annual temperature; degree-days < 0 °C; summer-winter temperature differential; and a moisture index, the ratio of degree-days > 5 °C to mean annual precipitation. Validation of the response functions with two sets of independent data produced for all functions statistically significant simple correlations with coefficients as high as 0.81 between actual and predicted heights. The response functions described the widely different growth potentials typical of natural populations and demonstrated that these growth potentials have different climatic optima. Populations nonetheless tend to inhabit climates colder than their optima, with the disparity between the optimal and inhabited climates becoming greater as the climate becomes more severe. When driven by a global warming scenario of the Hadley Center, the functions described short-term physiologic and long-term evolutionary effects that were geographically complex. The short-term effects should be negative in the warmest climates but strongly positive in the coldest. Long-term effects eventually should ameliorate the negative short-term impacts, enhance the positive, and in time, substantially increase productivity throughout most of the contemporary pine forests of Eurasia. Realizing the long-term gains will require redistribution of genotypes across the landscape, a process that should take up to 13 generations and therefore many years.     

Root system analysis of seedlings of seven tree species from a tropical dry forest in Mexico

Summary Root attributes of tree seedlings of seven species from the tropical deciduous forest along the Pacific Coast of Mexico are described using morphometirc root system analysis. Mean relative growth rate, root/shoot ratios, specific root length, root density, mean number of roots tips and root length/leaf area ratio were determined in seedlings grown for 35 days inside growth chambers. All the species had low relative growth rates, low root/shoot ratios and low root densities (<0.5 cm/cm³). The species associated with disturbed habitats, in contrast to the species characteristic of undisturbed areas, presented small seeds, a dichotomous root branching pattern and large specific root length. No relationship was found between seed size and mean relative growth rate among the species studied.     

西双版纳热带季节雨林土壤氮含量对乔木树种多样性的影响?

大气氮沉降或人类活动导致生态系统氮输入增加,可能会提高土壤氮含量水平,促进优势种的生长和减少环境异质性,从而使物种共存的生态位减少,群落物种多样性降低。为研究土壤氮含量的增加对森林群落乔木树种多样性的影响,本研究在西双版纳热带季节雨林随机设置了14个1 ha的样方,对各样方土壤总氮( TN)含量、乔木树种丰富度以及西双版纳热带季节雨林20 ha动态监测样地中各样方乔木树种及建群种望天树( Parashorea chinensis)生物量进行了调查。结果表明：土壤氮含量与乔木树种丰富度具有显著负相关而与群落及建群种望天树生物量具有显著正相关。我们推测其机制可能是：土壤氮含量增加促进了建群种望天树等的生长及群落生物量的积累,减少树种共存的生态位,由于竞争排斥等原因而导致群落树种丰富度降低。因此,减少生态系统人为氮输入,对于保护西双版纳热带季节雨林乔木树种多样性具有重要意义。     

Structural comparison of tropical montane rain forests along latitudinal and altitudinal gradients in south and east Asia

Geographical patterns of altitudinal zonation, floristic composition, and structural features of tropical montane rain forests were examined along latitudinal gradients in south and east Asia. On equatorial mountains, the tropical montane rain forests occur above 1000 m. Toward middle latitudes, they come farther down and reach sea level at c. 35° N. Thus, the forests are equivalent to the subtropical rain forests of the latitudinal, horizontal zonation series. They exhibit gradual changes in floristic composition and structure along both altitudinal and latitudinal gradients. On equatorial mountains, they are divided into three types, i.e. tropical lower montane, upper montane, and subalpine forests. The three tree regeneration types, having emergent, sporadic and inverse-J type stem-diameter class frequency distributions, coexist in the lower montane forests, but the upper and subalpine forests display only the inverse-J type species with a few species of the sporadic type. Toward the northern latitudinal limit, the distinction between the three tropical montane forest zones in equatorial mountains becomes less clear. This can be explained by temperature conditions: on equatorial mountains, a temperature sum of 85° C months which controls the upper limit of the lower montane forests, and a coldest month mean temperature of-1° C which controls the evergreen broad-leaved trees, appear at c. 2500 and c. 4000 m respectively. The altitudinal range between 2500 m and 3800 m, which is the upper forest limit, is covered by upper montane and subalpine forests. On the other hand, at the latitudinal northern limit, the tropical upper montane and subalpine forests cannot exist because the above mentioned two temperature conditions occur at nearly the same point. Thus, at the northern latitudinal limit of the tropical montane forests, the three zones of equatorial mountains amalgamate into a single subtropical lowland forest community. This is due to the seasonal temperature climate in middle latitudes in, e.g., central Japan and central China.A part of this paper was presented as an oral presentation at the Vth International Congress of Ecology, Yokohama 23–30.8.1990.