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Population structure and distribution pattern of Pinus tabulaeformis in Wulashan natural reserve of Inner Mongolia
Abstract
Pine community is one of the most important community types in Wula Mountain which is a large water conservation area in western Inner Mongolia Autonomous Region. There is great significance to master the pine population structure and distribution patterns for the health assessment and management of mountain forest ecosystem in arid and semi-arid areas. By studying the distribution characteristics of natural pine (Pinus tabulaeformis Carr.) population in Wula Mountain Nature Reserve, three representative samples were set up and the age structure and spatial distribution patterns of the pine populations were studied by using the population diameter instead of the age class structure and point pattern analysis (Ripley's K-Function) methods. The results showed that the age structure of pine population was at different developmental stages due to pine's own biological characteristics, environmental factors and human interference. Overall, the age structure of pine population was at the stable type in Wula Mountain. The survival curve of natural pine populations was close to Deevey II type. In addition, the natural pine populations showed different distribution patterns under different age structure and habitat conditions. Under suitable growth environment (shady slope and semi-shady slope at altitude 1400-1800 m) and population were dominated by middle-aged and young trees, the population showed a cluster distribution. The population distributed at high altitude (1 800 m and above) and sunny stony slope were usually older and with lower density and the population spatial pattern was characterized by a random distribution.
... In addition, these results describe an ecological pattern in which the trees in Chinese pine forests are arranged randomly. Other researchers have found that the tree distribution pattern in Chinese pine forests changes constantly among different growth and development stages [35,43]. ...
The Chinese pine (Pinus tabulaeformis Carr.) is an ecologically and economically important evergreen coniferous tree which dominates warm temperate forests throughout northern China. We established two permanent plots within the Chinese pine forest in the Jiulong Mountains, Beijing, China. To understand the structural characteristics and dynamics of these plots, we analyzed the spatial structural characteristics within nearest-neighbor relationships using the bivariate distributions of the stand spatial structural parameters: uniform angle index, W; mingling index, M; dominance index, U; and crowding index, C. Results revealed that most trees in the forest were randomly distributed. The predominant individuals and randomly arranged trees were in very dense areas and surrounded by the same species. In addition, both plots exhibited a uniform size differentiation pattern. The two plots differed mainly in the level of species mixture and dominance. The majority of reference trees in the pure Chinese pine forest (plot 1) exhibited poor species mingling and low dominance, whereas trees in the mixed Chinese pine forest (plot 2) were evenly distributed in each mingling class and most trees were of intermediate dominance. The study results are useful for optimizing forest management activities in the studied stands, promoting tree growth, regeneration and habitat diversity, and improving forest quality at a fine scale.
We studied forest structure and composition along a chronosequence of secondary forest succession in Northwest Argentina's montane forests (‘Yungas’) at 27°S, between 700 and 900 m. Early herbaceous stages, forested stages of 11, 25, 45, and 50 years after abandonment, and old-growth forests were surveyed. Secondary forests included stands that originated in abandoned herbaceous crops and in abandoned fruit orchards. Basal area and species composition differed between 50-year-old secondary forests and old-growth forests. In contrast, tree density and species diversity were similar in the 50-year-old and in the old-growth forests. The previous use (herbaceous crops or fruit orchards) was an important influence on secondary forest composition. Whereas stands originating in herbaceous fields were dominated by wind-dispersed native species such as Heliocarpus popayanensis, Tecoma stans, Parapiptadenia excelsa, and Tipuana tipu, fruit-orchard-originated stands were dominated by animal-dispersed species. Among the animal-dispersed species, the exotic tree Morus alba was the most abundant, and its abundance in secondary forests seems to slow the succession toward old-growth forest composition. Overall, after accounting for differences attributable to pre-abandonment conditions, secondary forest succession showed a trend toward compositional convergence, with the rate of succession apparently regulated by the demography of long-lived pioneer species.
1 The age, diameter and position of all living ($n = 750$) and dead $(n = 286)$ stems of a northern clone of Populus balsamifera were recorded to study spatial dispersion patterns and to reconstruct clonal development. Position, age and diameter of all Picea spp. stems found within the study area were also recorded. Spatial autocorrelation analyses were performed on the data using age and diameter as variables. 2 Results from spatial analyses suggest that P. balsamifera stems could be classified into three age groups, each one with a distinct spatial pattern: younger stems (
The tree population size structure and relationship between tree diameter and age were examined in a subalpine fen and surrounding Picea-Abies forest in northern Colorado. The fen grades from a sedge fen, through an ecotone, to a treed fen. Tree growth rate varies across the vegetational gradient, with the sedge fen having the slowest growth, and the upland forest having the fastest growth. Differences in growth rate are related to the average size of peat hummocks, with areas containing tall hummocks exhibiting the highest tree growth rates. Size structures display the characteristic reverse-J distribution generally indicative of stable populations, but forest vegetation is expanding into the open regions of the fen, and within the treed fen an increase in Abies lasiocarpa is occurring. These changes are primarily attributed to a positive feedback situation wherein the fen's surface is built up by peat accumulation. Distinct hummocks form first on the open fen but then coalesce to form raised peat islands in the treed fen. This new substrate provides habitat with a comparatively low water table and allows the growth of mesophytic forest vegetation. A pathway for this vegetational development is proposed.
We investigated the population structure and spatial pattern of major trees in a subalpine old-growth coniferous forest stand in the Ontake Forest Reserve of central Japan to examine the coexistence strategies of different species. We mapped all stems ≥5 cm in diameter at breast height (dbh) on a 2 ha plot. The stand contained nine woody plant species and 1508 living stems with a combined basal area of 55.6 m2 ha−1. The four major species were divided into two groups based on density and size/age structure. Group A (Abies mariesii and Abies veitchii) had a lower maximum age and higher density than group B, as well as reverse J- or L-shaped dbh distribution of live stems. Species in group B (Picea jezoensis var. hondoensis and Tsuga diversifolia) had very few stems in the understory, higher maximum ages than group A, and bell-shaped dbh distributions. Group B species may compensate for having fewer stems in the understory by having a longer lifespan, while species in group A may compensate for lower longevity by having numerous young stems in the understory. Canopy and understory stems of the four major coniferous species were patchily distributed throughout the plot. The distribution of canopy stems of species in group B was negatively associated with that of group A, but positively associated with understory stems in their own group. Similarly, the distribution of canopy stems of species in group A was negatively associated with that of understory stems of group B species. These results suggest species differences in favourable canopy and forest floor condition. Differences in life history strategies and site preferences may explain the coexistence of these species.
The population structure of three dioecious species, Diospyros montana, Diospyros sylvatica and Garcinia talbotii was studied in a seasonal cloud forest in the Western Ghats of India. In an undisturbed, natural population of D. montana, female fecundity was not significantly influenced by distance to neighbours or by flower numbers on neighbours. In the same population fruit set was also unrelated to the angular dispersion of neighbours. On the other hand, in an altered population of this species in which conspecifics are extremely isolated due to human activities, insect visitation and fruit set were strongly and negatively correlated with distance to the nearest male. Moreover, the number of insects and fruit set in the natural population were significantly higher in the natural population than in the altered population. In the natural population, trees of large girth produced larger numbers of flowers in both sexes and females which produced larger numbers of flowers, also produced more fruits and fruit set (fruits/flower). In the altered population, fruit numbers and fruit set in female trees were unrelated to the flower numbers, which is possibly due to pollination limitation as a result of inadequate pollinator visits at female trees. Sex ratios were male-biased (3.7:1) in the natural population and female-biased (1:2) in the altered population of D. montana, as well as in G. talbotii (1:3.8) and D. sylvatica (1:12.2) populations where the lower girth classes are mainly cut. The girth class distribution of G. talbotii and D. sylvatica populations was skewed towards larger girths suggesting that future recruitment will be severely affected.