Structure and species diversity of subtropical evergreen broad-leaved forest in northern Okinawa Island, Japan

The structure and tree species diversity of a subtropical evergreen broad-leaved forest in northern Okinawa Island, Japan, were studied. Enumeration of the six sampling plots revealed an average density of 5,580 individuals with DBH≧3.0 cm/ha, having an average basal area of 55 m². The large-size trees of DBH≧20 cm contributed 10% of the total individuals, and 49% of the total basal area. The forest showed a high diversity of tree species, which is comparable to some tropical rain forests. A total of 54 over-story species of 24 families and a total of 63 understory species of 26 families were identified in the six sampling plots. Fagaceae and Theaceae were the most important families;Castanopsis sieboldii, Schima wallichii andDistylium racemosum were the most important species. The diversity index and equitability index of species were 4.15 and 0.72 for the overstory plots, and 4.72 and 0.79 for the understory subplots, respectively. The diversity index for the overstory was significantly correlated to the total basal area of trees over 20 cm DBH (p<0.05) and the importance value ofC. sieboldii (p<0.001), while for understory, the diversity index was not correlated to the structural parameters (allp>0.16). The size distribution pattern and age structure indicated differences in regeneration strategies for canopy dominants. In population dynamics of the succession process,C. sieboldii andD. racemosum were self-maintaining types, andS. wallichii was a gap- or opening-dependent type. This study was made possible by support from the Japanese Ministry of Education, Sciences, Sports and Culture, which provided a Monbusho scholarship to X.N. Xu.     

Effect of selective logging on stand structure and tree species diversity in a subtropical evergreen broad-leaved forest

?Context

Selective logging followed by natural regeneration is rarely employed for restocking subtropical evergreen broad-leaved forests in East Asia compared with the use of clear-cutting.

?Aims

To clarify the succession of these forests, the effects of selective logging on stand structure, species diversity, and community similarity were studied in a mature and regenerating forest in Okinawa, Japan.

?Methods

Four study plots were established, and trees ≥1.2 m height were identified by species name, tree height, and diameter at breast height.

?Results

The results showed that the species composition of regenerating forest was similar to mature forest; however, the former had a greater species density and Shannon–Wiener index than the latter. Castanopsis sieboldii and Distylium racemosum, the predominant trees in the mature forest, continued to dominate the regenerating forest, with a broad layer distribution. High Sørensen and Jaccard community similarity indices for mature and regenerating forest indicated that the regeneration occurred in a progressive succession.

?Conclusion

The similar species composition and stand structure for both mature and regenerating forest, and the higher species diversity for the latter, provided no evidence of forest degeneration and suggested that the regenerating forest may develop into a stand similar to preselective logging forest.     

亚热带常绿阔叶林结构、树种多样性和土壤特性的研究(英文)

采用样地调查法,对日本冲绳岛北部的亚热带常绿阔叶林的林分结构,树种组成以及土壤特性等进行了调查分析。结果表明,该亚热带林具有林冠低矮、小径木多等特点。林分的平均林冠高度仅10m,平均立木密度达5400株·hm2(≥3.0cmDBH),其中胸径小于10cm的立木占64%。林分胸高断面积为54.4m2·hm-2。30个调查样地共出现树种数(≥3.0cmDBH)达80种,分属31个科。根据树种的重要值,Castanopsis sieboldii和Schima wallichii分别为优势树种和亚优势树种。树种多样性指数(H’)平均达3.63,均衡度指数(J’)为0.71,丰富度指数(S’)为4.72。这些多样性指数都随着优势树种重要值的增加而显著降低。土壤养分测定结果表明,该森林的土壤肥力低,异质性大,并可能存在Al毒害。由相关分析知,林分密度和优势树高均与土壤pH值呈显著正相关关系;多样性指数则与土壤交换性K ,Ca2 以及Ca2 /Al3 比呈显著的正相关,而与土壤有机碳,全氮和磷呈显著的负相关。这些结果说明土壤性质是影响冲绳亚热带常绿阔叶林林分结构和树种组成多样性的重要因素。图3表4参38。     

Sprouting characteristics of a subtropical evergreen broad-leaved forest following clear-cutting in Okinawa,Japan

This study explores the sprouting characteristics of an evergreen broad-leaved forest after clear-cutting based on a survey of 1,893 stumps of 62 tree species in Okinawa, Japan. The sprouting capabilities of the stumps varied among tree species. The stumps of 60 species could produce sprouts, while those of the other two species could not. In 10 of the sprouting species, the mean sprout-stem number was higher than 4.0 stems per stump; nine sprouting species showed low sprouting capabilities. Additionally, Castanopsis sieboldii and Schima wallichii, the dominant species, exhibited high sprouting capabilities. Further, the sprouting capabilities varied with stump diameter at breast height (DBH). Stumps with a larger DBH tended to have a higher mean number of sprout stems per stump, higher DBH, and higher tree height than the smaller stumps. The forest stands regenerated by sprouting might recover into a tree community similar to that before clear-cutting.     

Ecological studies on subtropical evergreen broad-leaved forest in Okinawa, Japan: Litter production and nutrient input

Patterns of litterfall and nutrient input in a subtropical evergreen broad-leaved forest in northern Okinawa, Japan, were studied during May, 1996–April, 1999. The mean annual rate of litterfall in the five sampling plots ranged from 6.84 to 8.93 Mg ha⁻¹ yr⁻¹, of which 63.3–68.5% were leaves; 22.4–29.1% woody parts (including branches < 5.0 cm in diameter and bark); 2.8–5.0% sexual organs and 4.6–6.3% miscellaneous material. Significant differences were found among plots and among years. Significantly monthly differences pronounced seasonal patterns in litterfall were observed. Total litterfall and leaf litter showed negative correlations with relative basal area of the dominant species,Castanopsis sieboldii; and showed positive correlations with mean height of the stands. The dominant species,C. sieboldii produced an average of 2.36 Mg ha⁻¹ yr⁻¹ of leaf litter, which covered 30.5% of the annual litter production, and the nutrient input from those litterfall contributed 32.3, 28.3, 30.2, 22.2, 32.5, and 30.5% of total N, P, K, Ca, Mg, and Na, respectively. Nutrient use efficiency in litter production was high, especially for P and K compared with other broad-leaved forests in Japan indicating that P and K may be limiting in Okinawan evergreen broad-leaved forest.     

Effects of selection cutting on the forest structure and species diversity of evergreen broa-leaved forest in northern Fujian, southern China

The short-term effects of selection cutting of different intensities on the forest structure and species diversity of evergreen broad-leaved forest in northern Fujian Province were investigated and analyzed. The results showed that selection cutting of low and medium intensities caused little variation in the forest structure. After cutting, the dominant species retained their leading status in the community. However, the community structure changed significantly following selection cutting of high and extra-high intensities; the status of the dominant species of the community declined dramatically. Some tree species began to disappear from the sampling plots. Except for extra-high intensity cutting, the diversity of tree species did not change significantly for the other three cutting intensities. However, the evenness of the stands was very different among the four kinds of cutting plots. For low and medium intensity selection cutting, the evenness declined slightly. For extra-high intensity selection cutting, the evenness increased to some extent, which might be due to a more even distribution of tree species after cutting. Cutting operations resulted in some adverse reactions to development of arborous species diversity of evergreen broad-leaved forest, particularly serious damage to the forest canopy. But the rational selection cuttings, which may benefit the restoration and maintenance of species diversity over a long period and may come about from the variations in environmental factors such as sunlight, temperature and humidity.     

Effects of selection cutting on the forest structure and species diversity of evergreen broad-leaved forest in northern Fujian, southern China

The short-term effects of selection cutting of different intensities on the forest structure and species diversity of evergreen broad-leaved forest in northern Fujian Province were investigated and analyzed. The results showed that selection cutting of low and medium intensities caused little variation in the forest structure. After cutting, the dominant species retained their leading status in the community. However, the community structure changed significantly following selection cutting of high and extra-high intensities;the status of the dominant species of the community declined dramatically. Some tree species began to disappear from the sampling plots. Except for extra-high intensity cutting, the diversity of tree species did not change significantly for the other three cutting intensities. However, the evenness of the stands was very different among the four kinds of cutting plots. For low and medium intensity selection cutting, the evenness declined slightly. For extra-high intensity selection cutting, the evenness increased to some extent,which might be due to a more even distribution of tree species after cutting. Cutting operations resulted in some adverse reactions to development of arborous species diversity of evergreen broad-leaved forest, particularly serious damage to the forest canopy. But the rational selection cuttings, which may benefit the restoration and maintenance of species diversity over a long period and may come about from the variations in environmental factors such as sunlight, temperature and humidity.     

Resilience of stand structure and tree species diversity in subtropical forest degraded by clear logging

Subtropical forests in the Ryukyu Islands have been degraded by silvicultural practices, and thus their structural attributes are being shifted to other states dominated by a few tree species. This study clarified the mechanisms of the change, and examined the effect of clear logging on the resilience of a subtropical forest. Sprouting regeneration and typhoon disturbance were introduced into an individual-based model, SEIB-DGVM, for describing stand development and succession. The regeneration dynamics from young secondary to old-growth stands were reproduced fairly well with the model. Sprouting recruitment produced high stem density at the beginning of stand development, which caused a self-thinning trajectory following the −3/2 power law. In the late development stage after 70 years, tree species diversity fluctuated because of the regenerative response of sprouting species and the facilitatory effect of typhoon disturbance on the coexistence of subordinate species. The death of canopy trees because of typhoon disturbances reduced the dominance of Castanopsis sieboldii, and depressed its dominance in the understory. Consequently, the understory species could establish by virtue of fallen canopy trees, and tree species diversity increased at the stand level. Clear logging experiments in the model revealed that species diversity deteriorated, especially in the stand dominated by sprouting species. Resilience of subtropical forests was determined by initial species composition before clear logging. Our simulation results suggest that repeated logging drives subtropical forests with high species diversity to a stand monopolized by C. sieboldii.     

Biomass,and carbon and nitrogen pools in a subtropical evergreen broad-leaved forest in eastern China

Subtropical evergreen broad-leaved forest is the most widely distributed land-cover type in eastern China. As the rate of land-use change accelerates worldwide, it is becoming increasingly important to quantify ecosystem biomass and carbon (C) and nitrogen (N) pools. Above and below-ground biomass and ecosystem pools of N and C in a subtropical secondary forest were investigated at Laoshan Mountain Natural Reserve, eastern China. Total biomass was 142.9 Mg ha⁻¹ for a young stand (18 years) and 421.9 Mg ha⁻¹ for a premature stand (ca. 60 years); of this, root biomass was from 26.9 (18.8% of the total) to 100.3 Mg ha⁻¹ (23.8%). Total biomass C and N pools were, respectively, 71.4 Mg ha⁻¹ and 641.6 kg ha⁻¹ in the young stand, and 217.0 Mg ha⁻¹ and 1387.4 kg ha⁻¹ in the premature stand. The tree layer comprised 91.8 and 89.4% of the total biomass C and N pools in the young stand, and 98.0 and 95.6% in the premature stand. Total ecosystem C and N pools were, respectively, 101.4 and 4.6 Mg ha⁻¹ for the young stand, and 260.2 and 6.6 Mg ha⁻¹ for the premature stand. Soil C comprised 23.8–29.6% of total ecosystem C whereas soil N comprised 76.9–84.4% of the total. Our results suggest that a very high percentage of N in this subtropical forest ecosystem is stored in the mineral soil, whereas the proportion of organic C in the soil pool is more variable. The subtropical forest in eastern China seems to rapidly accumulate biomass during secondary succession, which makes it a potentially rapid accumulator of, and large sink for, atmospheric C.     

Stand structure and plant species occurrence in forest edge habitat along different aged roads on Okinawa Island, southwestern Japan

We compared stand structure and plant species occurrence on the shoulders of 3-, 10- and 20-year-old roads in a subtropical evergreen broad-leaved forest to document temporal changes in edge effects of forest roads. We recorded 154 vascular species in the study plots, including 3 non-native species. We used generalized linear mixed models to analyze changes in forest structure and plant species composition in relationship to the distance from forest roads. The spatial patterns in stand structure at different distances from roads differed with road age. The large canopy openness on the edge of 3-year-old roads decreased with time after the construction. A progressive decrease in tree height on roadsides was observed after the road construction, suggesting tall trees could not withstand the dry and windy roadside environment. The edge effect on the canopy tended to be larger at higher elevation sites. The spatio-temporal pattern of species occurrence based on distance from roads differed by species. Typical pioneer species such as Schima wallichii and Eurya japonica increased along the edge, while less aggressive pioneer species and understory species decreased. As time passed after the road construction, some climax and understory species decreased at the forest edge, while other climax and understory species increased. The modeling methods proposed in this study could be applied to different roadside and edge study sites.     

Effects of a severe typhoon on forest dynamics in a warm-temperate evergreen broad-leaved forest in southwestern Japan

The effects of a typhoon on forest dynamics and the response of major tree species were studied in a warm-temperate evergreen broad-leaved forest in southwestern Japan. The strongest typhoon on record (T9313) passed through this region in 1993. Return periods of typhoons over 30 ms⁻¹ in instantaneous wind velocity and T9313 were estimated to be 2.2 and 104.5 years, respectively. Approximately 10% of all stems suffered some damage from T9313 and annual stem mortality rose from 1.3 to 2.7%. The estimated period that the number of stems would fall below 10% of the initial was four years shorter with T9313-class typhoons than without them. Thus, the disturbance by T9313 was not catastrophic at the site although T9313 was an episodic typhoon. The short-term responses of major tree species to T9313 were classified into four types: 1) blunt-response type with little decrease and recruitment of stems in the DBH ≥ 5 cm class (Distylium racemosum), 2) retreat type with larger decrease than recruitment (e.g. Quercus acuta), 3) sharp-response type with a large decrease and much recruitment (e.g. Cinnamomum japonicum), and 4) advance type with less decrease than recruitment (Eurya japonica). Among the four regeneration types classified by previous studies (climax, light-demanding, subcanopy, and few-sapling), the climax and few-sapling types each showed a specific short-term response, the blunt-response and retreat types, respectively, that explains one aspect of the regeneration strategies of each type. On the other hand, the light-demanding or sub-canopy type showed multiple short-term responses, indicating that each regeneration type contains species with various regeneration strategies. In this paper, I analyzed data from the database that was compiled by the Aya Research Team.     

Long-term ecological impacts of clear-fell logging on tree species diversity in a subtropical forest,southern Japan

Defining the spatial arrangement and length of the cutting cycle in a logged area is crucial for reconciling potential conflicts between timber yields and maintenance of ecosystem services in natural forests. In this study, we investigated long-term impacts of clear-fell logging on timber production and tree species diversity in a subtropical forest on the Ryukyu Islands, using an individual-based simulation model. We assumed six logging scenarios defined by combinations of forest type and regeneration processes, which acted as surrogates for spatial scales of clear-fell logging. These scenarios were simulated under cutting cycles ranging from 20 to 150 years. Short-cutting cycles resulted in dominance by the sprouting species Castanopsis sieboldii. The compositional shift was accelerated by the lack of seed dispersal from surrounding forest areas. The simulations demonstrated that a sustainable logging regime maintaining both yield and tree species diversity requires a cutting cycle longer than 50 years. The simulation results also suggest that the trade-off between the recovery of tree species diversity and timber production is favored more in stands surrounded by mature forest than in isolated stands or stands surrounded by immature forest. Ecological risk assessments based on model simulations provide an alternative to current forest management practices that rely on empirical knowledge.     

Photosynthetic nitrogen-use efficiency in evergreen broad-leaved woody species coexisting in a warm-temperate forest

Photosynthetic nitrogen-use efficiency (PNUE, photosynthetic capacity per unit leaf nitrogen) varies among species from different habitats and correlates with several ecological characteristics such as leaf life span and leaf mass per area. We investigated eight evergreen broad-leaved woody species with different leaf life spans that coexist in a warm-temperate forest. We determined photosynthetic capacity at ambient CO(2) concentration in saturated light, nitrogen concentration, and the concentration of ribulose-1,5-bisphosphate carboxylase (RuBPCase), a key enzyme of photosynthesis and the largest sink of nitrogen in leaves. Each species showed a strong correlation between photosynthetic capacity and RuBPCase concentration, and between RuBPCase concentration and nitrogen concentration. Photosynthetic capacity of leaves decreased with increasing leaf life span, whereas PNUE did not correlate significantly with leaf life span. There was a twofold variation in PNUE among species. This relatively small variation in PNUE is consistent with the argument that species that coexist in a single habitat maintain a similar PNUE. The two components of PNUE-photosynthetic rate per unit RuBPCase and RuBPCase per unit leaf nitrogen-were not significantly correlated with other leaf characteristics such as leaf life span and leaf mass per area. We conclude that differences in PNUE are relatively small among coexisting species and that differences in absolute amounts of photosynthetic proteins lead to differences in photosynthetic productivity among species.     

万佛山丹霞地貌区常绿阔叶林群落物种多样性分析

为探讨丹霞地貌区常绿阔叶林群落物种多样性,通过对物种丰富度指数、物种相对多度模型、物种多样性指数和物种均匀度指数的测度,对区域内16个常绿阔叶林群落进行分析,并与中亚热带典型地区森林群落物种多样性比较。结果表明,万佛山常绿阔叶林群落具有较高的物种丰富度,物种多样性在层次中的变化趋势为灌层〉乔层〉草层;万佛山常绿阔叶林生物多样性在中亚热带常绿阔叶林生态系统中具有普遍的意义。     

Coldness index does not indicate the upper limit of evergreen broad-leaved forest on a subtropical island

Many ecologists in East Asia consider that Kira’s coldness index (CI) of ?10 °C month agrees well with the northward and upward limits of evergreen broad-leaved forest (EBLF). It is of interest to establish whether CI is an effective indicator of the upper limit of EBLF in a tropical-to-temperate transitional island. A case study in Taiwan was conducted through a comparison of CI layers with field vegetation information. The results from spatial analysis revealed that the location of CI = ?10 isotherm was approximately 3,381 m a.s.l., within the Abies zone. The analysis of plots showed that vegetation near CI = ?10 isotherm was evergreen coniferous pure forest with 99.9 % relative dominance. The CI = 0 isotherm lay at approximately 2,594 m a.s.l., close to the boundary between the Tsuga–Picea and upper Quercus zones, with the CI = 0 isotherm in the transformation zone between evergreen coniferous and broad-leaved trees. However, the vegetation near CI = 0 isotherm tended more toward coniferous forest showing a total relative dominance of 78.26 %. The two-way cluster dendrogram of vegetation plots revealed identical results. The preceding evidence, combined with the spatial pattern of 3,564 plots along CI and elevation gradients, made it clear that CI did not indicate the upper limit of EBLF in Taiwan. Other information on the CI criterion are discussed. To explore the differentiation of altitudinal vegetation, further research should be made to connect ecoclimatic factors such as effective warmth index with information from vegetation plots.     

Seed rain,soil seed bank,seed loss and regeneration of Castanopsis fargesii (Fagaceae) in a subtropical evergreen broad-leaved forest

Understanding the seed rain and seed loss dynamics in the natural condition has important significance for revealing the natural regeneration mechanisms. We conducted a 3-year field observation on seed rain, seed loss and natural regeneration of Castanopsis fargesii Franch., a dominant tree species in evergreen broad-leaved forests in Dujiangyan, southwestern China. The results showed that: (1) there were marked differences in (mature) seed production between mast (733,700 seeds in 2001) and regular (51,200 and 195,600 seeds in 2002 and 2003, respectively) years for C. fargesii. (2) Most seeds were dispersed in leaf litter, humus and 0–2 cm depth soil in seed bank. (3) Frequency distributions of both DBH and height indicated that C. fargesii had a relatively stable population. (4) Seed rain, seed ground density, seed loss, and leaf fall were highly dynamic and certain quantity of seeds were preserved on the ground for a prolonged time due to predator satiation in both the mast and regular years so that the continuous presence of seed bank and seedling recruitments in situ became possible. Both longer time observations and manipulative experiments should be carried out to better understand the roles of seed dispersal and regeneration process in the ecosystem performance.     

江西金盆山林区天然常绿阔叶林生态系统碳储量研究

【目的】探讨亚热带典型天然常绿阔叶林碳储量及其碳分布格局,以期为常绿阔叶林生态系统碳汇功能评价提供基础数据和理论依据。【方法】以江西省金盆山林区优势树种生态系统生物量研究为基础,结合主要优势树种碳含量实测数据,对金盆山典型常绿阔叶林丝栗栲林、南岭栲林、米槠林的碳储量及碳空间分布格局进行研究,并以这3种林分的碳密度均值计算整个金盆山林区天然常绿阔叶林总碳储量。【结果】金盆山林区丝栗栲林、南岭栲林、米槠林生态系统碳密度分别为294.82、307.63、318.97 t/hm^2,林区生态系统总碳密度为307.14 t/hm^2,林区现存碳总量为2.25×10^6 t;生态系统碳密度分布规律为植被层>土壤层>凋落物层,植被层碳密度分布规律为乔木层>灌木层>草本层,其中乔木层主干的碳密度占56.54%;土壤层碳密度随着土壤层的加深呈下降趋势,40 cm以下土层间的碳密度变化不明显。【结论】金盆山林区常绿阔叶林不同林分间生态系统碳密度差异不显著,生态系统内碳密度有较强的空间分布规律,生态系统碳密度高于我国森林生态系统平均碳密度和多种典型森林类型碳密度,具有较强的碳汇功能。     

Productivity of temperate broad-leaved forest stands differing in tree species diversity

? Understanding the effects of tree species diversity on biomass and production of forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth forests is not well understood.

? We quantified biomass and above-ground production in nine forest stands with increasing tree species diversity from monocultures of beech to stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed stands are more productive than monospecific stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use.

? Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed stands.

? We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous forests depend more on tree species-specific traits than on tree diversity itself.