Forest In Southwestern China Research Articles

Distribution of carabid beetles among 40-year-old regenerating plantations and 100-year-old naturally regenerated forests in Southwestern China

Effects of reforestation by native tree species on species assemblages of carabid beetles were studied between 40-year-old regenerating plantations and 100-year naturally regenerated forests in Southwestern China. Two old naturally regenerated forest types (ca.100 years old) were chosen: hemlock-spruce forests ( Tsuga chinensis and Picea brachytyla) and birch forests ( Betula albo-sinensis). Three young regenerating forest types (ca. 40 years old), including spruce plantations ( P. brachytyla), larch plantations ( Larix kaempferi and Larix mastersian), and natural broad-leaved forests, were established after the logging of the old naturally regenerated forests. Using pitfall traps, we compared the distribution of carabid beetles in the five forest types. Three replicated plots for each forest type were chosen, and each plot was investigated with four trap sites twice each month during the growing season (May to October) in 2004. Our results showed that species richness and abundance were significantly higher in the young regenerating forests than in the old naturally regenerated forests. Analysis of complementarity in carabid species lists across the forest ages and types showed that the old naturally regenerated birch forests had the lowest similarity with the young regenerating larch plantations, and the highest similarity was shown between the two young regenerating plantations. Although PCoA ordination grouped the carabid assemblages according to forest type and forest age, the overall similarity among all forest types was high. Moreover, quantitative character species analysis did not detect significant species associated with forest types and ages. Based on the specificity and fidelity, most carabid species were abundant in all habitats, and only a few species were restricted in one or two forest types. Multiple linear regression between the species richness, abundance and Shannon diversity of carabids and of five environmental variables showed that the cover of canopy and herbaceous layer, and the depth of leaf litter had significant effects in determining richness, abundance and diversity of carabid beetles. Thus, the young regenerating forests at the mature stage could provide an appropriate habitat for most forest species of carabids survived in adjacent old naturally regenerated forests and might replace the role in part of the old-growth forests in sustaining the diversity of carabid assemblages. But some species are still restricted in old naturally regenerated forests, so in order to protect the diversity of carabid assemblages, it is necessary to sustain the intact old naturally regenerated forests when reforesting with some native tree species following natural succession.

Structure and regeneration dynamics of three subtropical midmontane moist evergreen broad-leaved forests in southwestern China, with special reference to bamboo in the forest understories

Two midmontane moist evergreen broad-leaved forests on the Ailao Mountains, Yunnan, and one on Mount Emei, Sichuan, southwestern China were studied to characterize the forest structure and dynamics as manifested in size, age, canopy gaps, regeneration modes, and the survival of seedlings. The most dominant canopy trees were species of Lithocarpus and Castanopsis of Fagaceae along with species of Machilus of Lauraceae and of Schima of Theaceae. The vertical structures of the forests were multilayered. All the canopy species had multimodal-shaped size and age distributions. In each forest of the study sites, the mean size of a canopy gap, caused mainly by the death of canopy trees, was smaller than 65 m2. No surviving seedlings of Fagaceae species were found in understories having bamboo with a coverage greater than 25% in any quadrat of the three forests. The poor seedling bank in the study forests is apparently due to the presence of bamboo in the understory. The tree regeneration may be synchronously related to the bamboo flowering event (interval approximately 55–60 years).

Female Sex Pheromone of the Yunnan Pine Caterpillar Moth Dendrolimus Houi: First (E,Z)-Isomers in Pheromone Components of Dendrolimus spp

The Yunnan pine caterpillar Dendrolimus houi Lajonquière is a serious defoliator of coniferous forests in southwestern China. Gas chromatography-electroantennography (GC-EAG) analyses of extracts of female sex pheromone glands of D. houi moths revealed the presence of three compounds eliciting antennal responses. These were identified as (5E,7Z)-5,7-dodecadien-1-ol (E5,Z7-12:OH), (5E,7Z)-5,7-dodecadien-1-yl acetate (E5,Z7-12:OAc), and (5E,7Z)-5,7-dodecadienal (E5,Z7-12:Ald) by comparison of their GC retention indices, mass spectra, and EAG activities with those of synthetic standards. Average amounts of E5,Z7-12:OH, E5,Z7-12:OAc, and E5,Z7-12:Ald per calling virgin D. houi female were 14.7 +/- 12.9 ng (+/- SD), 5.8 +/- 5.4 ng, and 0.8+1.4 ng, respectively, in a ratio of 100:39.7:5.6. These three components were also collected from the headspace of calling virgin female moths by solid-phase microextraction (SPME). In addition, trace quantities of (Z)-5-dodecen-1-ol (Z5-12:OH), (5Z,7E)-5,7-dodecadien-1-ol (Z5,E7-12:OH), (5E,7E)-5, 7-dodecadien-1-ol (E5,E7-12:OH), (5Z,7E)-5,7-dodecadien-1-yl acetate (Z5,E7-12:OAc), (5Z,7Z)-5,7-dodecadien-1-yl acetate (Z5,Z7-12:OAc), and (5E,7E)-5,7-dodecadien-1-yl acetate (E5,E7-12:OAc) were tentatively identified in female pheromone gland extracts by selected ion monitoring GC-MS. Field trapping experiments showed that E5,Z7-12:OH, E5,Z7-12:OAc, and E5,Z7-12:Ald were essential for attraction of male D. houi moths. Traps baited with a 20:1:1 blend (alcohol/acetate/aldehyde) loaded on gray rubber septa were as effective as traps baited with virgin female moths. The optimum ratio of acetate to aldehyde was 1:1, and this ratio was more critical than the ratio of either compound to the alcohol. This represents the first example of (E,Z)-isomers in pheromone blends of Dendrolimus species.

Distribution of carabid beetles among regenerating and natural forest types in Southwestern China

Heterogeneity in species assemblages of carabid beetles was studied between regenerating larch plantations of different forest ages and natural deciduous broad-leaved forests in Southwestern China. Larch plantations that were dominated by the non-native tree species ( Larix kaempferi) interspersed with a small proportion of native tree species ( L. mastersian) were established after the clear-cutting of the natural deciduous broad-leaved forests. Using pitfall traps, we compared the distribution of carabid beetles in recently planted (5 years old), young (15 years old), mature plantation (45 years old) and adjacent natural deciduous broad-leaved forests (ca. 100 years old). Four replicated plots for each plantation and five replicated transects in natural broad-leaved forest were chosen, and each plot or transect was investigated with four trap locations twice each month during the growing season (May–October) in 2004. Our results showed that species richness, abundance and Shannon diversity were significantly higher in the natural forest than in the regenerating plantations. In addition, these indices were not significantly different in 15- and 45-year-old plantations but were higher than those in 5-year-old plantation. Principal coordinate analysis (PCoA) ordination grouped the carabid assemblages according to forest type and forest age, suggesting that there is a general pattern of recovery after logging. Moreover, indicator species analysis detected significant species associated with forest types and ages. Based on the specificity and fidelity, carabids can be distinguished into six species groups: habitat generalists, generalists in forests with closed canopy, specialists in natural broad-leaved forest, generalists in plantations with closed canopy, young closed canopy larch plantation-associated species and open canopy larch plantation-associated species. Multiple linear regression showed that the depth of leaf litter, the cover of canopy and shrub layer had significant effects in determining richness, abundance and diversity of carabid beetles. Therefore, the regenerating larch plantations, even mature plantations, could not replace the role of the natural deciduous broad-leaved forests in sustaining the diversity of carabid assemblages. Furthermore, establishments of large areas of relatively homogeneous larch plantations may have detrimental long-term effects on the composition and structure of carabid assemblages. Thus, it is important for us to understand the subtle variations in habitat and take appropriate actions for maintaining the invertebrate diversity before the logging of natural forests and establishments of plantations.

Regeneration patterns and tree species coexistence in old-growth Abies– Picea forests in southwestern China

We analyzed the population structure (size, age, spatial patterns) and radial growth patterns of Abies faxoniana Rehder & Wilson, Picea purpurea Mast., and Betula sp. to investigate the role of dwarf bamboo abundance, gap disturbance, and species life history on the coexistence of canopy dominants in old-growth forests in the Wang Lang Natural Reserve in southwestern China. Four stands were sampled with a single large plot (0.4–0.5 ha). There were fewer tree seedlings and saplings in the two plots with a dense bamboo understory, and A. faxoniana seedlings and saplings were much more abundant than those of P. purpurea. Picea purpurea and Betula sp. seedlings established more frequently on raised surfaces than those of A. faxoniana. Seedling density of A. faxoniana, and B. utilis was also higher beneath open than closed canopy conditions in the plots with little bamboo. Young A. faxoniana and Betula sp. trees were clumped at small to intermediate scales (25–900 m 2), which are scales of clumping consistent with past regeneration in canopy gaps. Frequent peaks in radial growth releases in the canopy trees in the plots suggest a prevailing regime of small-scale gap disturbances. In each plot, A. faxoniana tree density and basal area was greater than that of P. purpurea. Picea purpurea trees were present in a wide range of age-classes in each plot indicating a pattern of intermittent regeneration in each stand for at least 500 years. In contrast, Abies faxoniana were abundant in age-classes <250 years, and few A. faxoniana were >350 years old. Betula sp. were mainly <120 years old. Betula sp. and P. purpurea preferred different seed-beds than A. faxoniana for establishment and regeneration of A. faxoniana, and especially Betula, is associated with gaps. Longevity and high survivorship are key life history traits of P. purpurea that prevent its replacement by A. faxoniana. In Wang Lang, stable coexistence is maintained by differences in species regeneration niche, species demographic characteristics, and species responses to the gap disturbance regime.

Canopy tree development and undergrowth bamboo dynamics in old-growth Abies– Betula forests in southwestern China: a 12-year study

Interactions between forest canopy characteristics and plants in the forest understory are important determinants of forest community structure and dynamics. In the highlands of southwestern, China the dwarf bamboo Bashania fangiana Yi is an understory dominant beneath a mixed canopy of the evergreen Abies faxoniana (Rheder & Wilson) and the deciduous Betula utilis (D. Don). The goal of this study was to better understand the role of bamboo dominance, canopy characteristics, and periodic bamboo dieback on forest development. To achieve this goal, we measured tree seedling, tree saplings, and trees, forest canopy characteristics, and bamboo cover in permanent forest ( n = 4) and gap plots ( n = 31) in a mixed A. faxoniana and B. utilis forest in Sichuan, China. Dwarf bamboos died off in 1983 in the gap plots, and in three of the four forest plots. Forest development was assessed for the period 1984–1996. The seedling bank in forest and gap plots increased after bamboo die-off. A. faxoniana seedlings increased more than B. utilis in forest plots; the opposite pattern characterized gap plots. The proportion of seedlings on raised micro-sites on the forest floor also changed and new seedling were more abundant on the forest floor. By 1996, bamboo seedling cover and biomass had recovered to ca. 45% or their pre-flowering values. Rates of bamboo seedling recovery were faster beneath canopy gaps and deciduous trees than beneath forest or evergreen trees. Tree mortality exceeded recruitment in plots with dense bamboo; the opposite pattern was found in the plot with little bamboo. The mortality rate for B. utilis trees (2.4% year −1) was higher than that for A. faxoniana (0.8% year −1) and forests with dense bamboos became more open over the census period. Tree mortality was size-dependent and intermediate sized trees had the lowest rates of mortality. Stand basal area increased mainly due to greater basal area gain than loss for A. faxoniana. Interactions between tree species life history, canopy type, and bamboo life-cycles create heterogeneous conditions that influence tree and bamboo regeneration and contribute to the coexistence of A. faxoniana and B. utilis in old-growth forests in southwestern China.

Succession features and dynamic simulation of subalpine forest in the Gongga Mountain, China

The Gongga Mountain of eastern Tibet Plateau is a representative of the alpine regions with high peaks and deep valleys. Climate change over the last thousand years has controlled the dynamics of glacier and debris flow occurrence, which resulted in substantial changes in the mountainous environment. The authors surveyed the community structure of primary forests in Gongga Mountain and forest succession processes in woodland plots. The changing features in the subalpine environment are discussed in this paper. Tree species and sizes between the glacier shrinking areas and debris flow fans in Hailuogou Valley are compared. The pioneer species that settle in debris flow fans and the glacier shrinking areas areSalix spp. andPopulus purdomii. Abies fabri andPicea brachytyla are the climax tree species. The succession process of primary vegetation in Hailuogou (2700 ∼ 3200 m) can be divided into four stages: Slash surface (20~200 yr)→Salix-Populus seeding community (10~30 yr)→Populus-Salix sapling community (30~100 yr)→Populus-Abies mixed community (50~100 yr)→Abies-Picea climax In a natural and undisturbed environment, trees compete for light, water and nutrients. Disaster disturbance in mountains is a very important driving factor for regeneration of woody plants. Repeated destruction of forests by glacier movement or debris flows generated additional forest gaps that allow young plants to grow. In this study the Gongga Forest Succession Model (GFSM) was developed for simulation of forest community succession processes on different scales in Gongga Mountain. A soil succession module was added to the GFSM model to simulate soil formation and chemical element change of woodland. In order to represent major features of forests in Southwestern China, many field works has been done to identify ecological parameters of various trees in the subalpine region. On the basis of simulation of tree life history, the GFSM combines forest succession with soil change in both material components and nutrition content. The Monte-Carlo method was applied to simulate random weather fluctuation and the uncertainty of tree death. These modeled processes agreed with the field investigation results in this region. The elevation distribution of different tree species was also simulated; and the results are consistent with field observations of ecological features of tree species. The modeling approach reflects well the succession dynamics of primary forests in Southwestern China. These results are very useful for improving the management policies and prediction technology for restoration and conservation of primary forests in Southwestern China.

Bamboo regeneration after flowering in the wolong giant panda reserve, China

Giant panda Ailuropoda melanoleuca are obligate bamboo grazers that inhabit montane and subalpine forests in south-western China. Knowledge of factors influencing bamboo abundance is crucial for panda ecology and identifying how human activities change panda habitat. This study follows bamboo regeneration from seed over seven years in panda habitat in clearcut and closed forest. Bamboo seedling density was significantly lower in clearcuts in 1984, 1985, and 1990 than beneath forest, and few seedlings remain in clearcuts. It appears that bamboo will not replace itself in clearcuts, reducing the extent of bamboo forest for pandas. Beneath forest, bamboo seedlings take 15–20 years to grow back to full height.