Species distribution modeling (SDM) is currently the primary tool for predicting suitable habitats for species. In this study, we used Abies kawakamii, a species endemic to Taiwan. Being the only Abies species distributed in high mountains, it acts as an ecological indicator on the subtropical island. We analyzed a vegetation map derived from remote sensing and ground surveys using SDM. The actual distribution of A. kawakamii in Taiwan has a total area of 16,857 ha distributed at an altitude of 2700–3600 m, and it often forms a monodominant forest at 3100–3600 m with the higher altitude edge as a forest line. Exploring the potential distribution of A. kawakamii through MaxEnt showed that the suitable habitat was 73,151 ha under the current climate. Under the scenarios of temperature increases of 0.5, 1.0, 1.5, and 2.0 °C, suitable habitat for A. kawakamii will gradually decrease to 70.2%, 47.1%, 30.2%, and 10.0% of this area, respectively, indicating that A. kawakamii will greatly decline under these climate warming scenarios. Fire burning disturbance may be the most significant damage to A. kawakamii at present. Although A. kawakamii has been protected by conservation areas and its natural regeneration is in good condition, it rarely has the opportunity to migrate upwards during climate warming. We suggest that in the future, research on the natural regeneration and artificial restoration of A. kawakamii should be emphasized, especially in the forest line ecotone.

The spatial patterns of plant species reflect the competitive pressures on individuals. To generate Competition indices (CI), we measured the diameter at breast height (DBH), crown volumes (CV) and the distances between trees. In this study, Abies kawakamii were divided based on the dominant component of the understory (moss or bamboo) to (1) investigate the relationship between the CI and stand structural attributes (SSAs); (2) compare the inter- and intraspecies; CIs as well as living and dead individual CIs; and (3) examine the relationship between the DBH and CI. The current findings indicate that the understory composition affected the CI and SSAs. The interspecies CI was larger than the intraspecies CI when bamboo-dominated the understory. In contrast, the intraspecies CI was larger than the interspecies CI when the understory was dominated by moss. The CI of dead individuals was higher than that of live individuals due to the biological characteristics and regeneration needs of Abies. Additionally, sensitivity to the environment and available resources may exert more pressure on young individuals than mature individuals.

Abies kawakamii (Taiwan fir) typically constitutes pure forest distributed at 3,100–3,600 m above sea level in Taiwan. Its volume was first investigated in 1963 using aerial photography to identify the growing stock of the forest. In 1973, Taiwan Forestry Bureau established a fir volume estimation equation by considering Taiwan spruce and Taiwan fir stands. However, due to cutting natural forest is not permitted in Taiwan, it was difficult to reconstruct specific volume equation for Taiwan fir. We can only use and collect the uprooted trees as samples for this study by Typhoon Soudelor in 2015. We used these samples for estimation and used the remaining trees for verification and tested the suitability of six equations (models) for Taiwan fir volume estimation. We found that the Schumacher equation was suitable for juvenile trees, and the generalized combined-variable equation was suitable for semi-mature trees. The Schumacher equation (a logarithmic equation) and generalized combined-variable equation demonstrated the better suitability for volume estimation. However, when a juvenile was considered in the estimation, the generalized combined-variable equation provided underestimations. Thus, the Schumacher equation (V = aD^bH^c) was the better model for our test. The new tree volume estimation equation for Taiwan fir in the Mt. Xue region is presented as follows: $\mathrm{V}=0.00003663\times D^{1.6693}\times H^{1.4003}$.

The contributions of urban forests and green spaces to sustainable development have been confirmed. Meanwhile, cities worldwide have shown that investments in urban forestry can greatly contribute to citizens’ quality of life. This study was conducted in urban forests in the Dadu Terrace of Taichung City, central Taiwan, which were frequently disturbed by fires and had grassland severely invaded by Panicum maximum after the forest degraded. We sampled 46 plots in Dadu Terrace to understand the relationship between the soil seed bank and vegetation as well as to evaluate the feasibility of applying soil seed bank transfers for ecological restoration in Dadu Terrace. The grassland was dominated by Panicum maximum. Forest vegetation was distinguished by cluster analysis into five types, i.e., Ficus microcarpa type, Acacia confusa type, Litsea glutinosa type, Cinnamomum camphora type, and Trema orientalis type. In the aboveground survey, we recorded 141 vascular plants, including 129 seed plants and 12 ferns. There were 40 identified species of naturalized plants. A total of 29,914 seedlings were recorded in the soil seed bank, with an average seed density of 9634 seeds/m² and a total of 91 species. There were 40 species of naturalized plants, accounting for 90.9% of the total seed reserves. This showed that Dadu Terrace was severely affected by the invasion of naturalized species. The species number and seed reserves of woody plants of the Panicum maximum type were significantly lower than those of forest vegetation. The composition of the soil seed bank was dominated by naturalized plants, indicating that the high frequency of fire reduced the proportion of native species and woody plants in the soil seed bank. Acacia confusa type was the main forest type in Dadu Terrace. Although several woody species and seed reserves were in its soil seed bank, the naturalized proportions were even higher. Trema orientalis type was the secondary forest type in Dadu Terrace; it had the smallest forest area. However, it was the only vegetation type with a greater tree seed abundance than herbs and the lowest proportion of naturalized seed abundance. Trema orientalis type vegetation has a relatively high soil transfer value for ecological restoration but lacks diversity. Our results revealed that the characteristics of the soil seed bank of Dadu Terrace make it challenging to restore the grassland to the forest by natural succession. Therefore, we suggest that artificial restoration is necessary for Dadu Terrace.

Abies kawakamii (Hay.) Ito is an endemic species mainly distributed in Taiwan’s subalpine region with an elevation of 3,000–3,600 m above sea level. It is a significant ecological indicator species in high subtropical mountains regarding plant geography and climate change. Taiwan is an island in the Asian-Pacific region. Typhoons cause forest gaps belonging to small-scale disturbances in the forest ecosystem, which is critical in maintaining species diversity and forest regeneration. We set up seven long-term monitoring plots of Ab. kawakamii forest to investigate the stand structure, species composition, and environmental factors of Mount (Mt.) Xue in Shei-Pa National Park. Comparing tree numbers between two surveys in a decade. Most of the population structure of Ab. kawakamii showed a similar positive skewness distribution between the two surveys, indicating that the population of Ab. kawakamii forest in Mt. Xue would be stable. According to principal component analysis (PCA), population structure of Ab. kawakamii correlated with dominant understory species and saplings of Ab. kawakamii but may be related to their habitat condition, such as elevation. Death trees released space and resources as gaps in the subalpine forest, which initiated micro-succession in the Ab. kawakamii forest.

Fire is one of the principal factors influencing subalpine ecosystem succession. Species numbers and plant compositions are used to determine postfire disturbance, vegetation, structural change, and succession. Ecologists also integrate species diversity and mathematical models to enable researchers to obtain increasingly detailed insights into habitats during post-disturbance restoration processes. This study employed five species-abundance models, namely the niche preemption model, the broken-stick model, the log-normal model, the Zipf model, and the Zipf–Mandelbrot model, to perform fitting analysis on the abundance data of postfire species coverage in shrub grasslands near 369 Hut at Xue Mountain in Shei-Pa National Park, Taiwan. We performed the logarithmic transformation on plant-coverage areas for each period of postfire shrub-grassland succession, and then, based on histograms drawn for species–coverage distribution modes, the test results consistently showed normal distributions (p < 0.05). Species-coverage histograms measuring various periods showed that there were comparatively higher numbers of common species during postfire succession and that the numbers of rare species progressively increased. The fitting results of the five species-abundance models showed that although the most suitable abundance models for each period of postfire succession varied, the majority of these periods demonstrated decent fitting with respect to the Zipf–Mandelbrot model. These findings showed that fuel consumption provided nutrients in a manner that facilitated postfire regeneration. Moreover, dominant species, such as Yushania niitakayamensis, and Miscanthus transmorrisonensis, did not fully occupy growing spaces and resource availabilities; consequently, seeded species were able to grow.