Rain Forest In Taiwan Research Articles

Mediation of stemflow water and nutrient availabilities by epiphytes growing above other epiphytes in a subtropical forest

AbstractStemflow is the most importance source of water and nutrients to epiphytes growing on tree stems that lack access to canopy soils. Many host trees are inhabited by a large number of epiphyte species, often growing in close proximity. The nutrient and water relationships among such co‐occurring epiphytes are largely unknown. We examined stemflow quality and quantity before and after passing through a substrate‐forming epiphyte, Asplenium nidus, and two nonsubstrate‐forming epiphytes, Haplopteris flexuosa and Liparis nakaharai, in a subtropical rainforest in Taiwan. The results indicate that stemflow quantity decreased after passing through these epiphytes. The magnitude of decreases was large for H. flexuosa (63%) and L. nakaharai (74%) but minor for A. nidus (5.6%), possibly because the vertical leaves of the latter collected throughfall, compensating for the water they retained. There was an overall decrease in stemflow ion concentrations after passing through A. nidus, likely due to greater retention than leaching of ions, but an overall increase after passing through L. nakaharai and H. flexuosa, possibly the result of greater leaching than retention. Our results indicate that epiphytes growing under A. nidus received more stemflow with few nutrients and those growing under the two nonsubstrate‐forming epiphytes received less stemflow but with more nutrients. Currently, the growth of epiphytes is limited by water at the study site, so that Asplenium provides favourable microhabitat for epiphytes growing below. If climate change lead to drier conditions, substrate‐forming epiphytes could become oases in the forest canopy desert and attract more epiphytes to grow underneath.

Net nitrogen mineralization and nitrification of different landscape positions in a lowland subtropical rainforest in Taiwan

Measurements of soil nitrogen (N) transformation rate are needed to be able to assess the plant availability and forest ecosystem losses of N, but little is known about lowland subtropical rainforests. The objectives of the present study were to determine the rates of N mineralization and nitrification in different seasons (January and August 2006) and in different landscape positions (footslope and summit) in the Nanjenshan forest of southern Taiwan, where vegetation types and soil properties vary among different landscape positions. Net N mineralization and nitrification were measured using 28-day in-situ open core and capped core incubations. The results from January 2006 showed that the concentrations of ammonium-N (NH4 +-N), mineral N (NH4 +-N plus NO3 −-N) and nitrate-N (NO3 −-N) were not significantly different between open and capped cores, or between summit and footslope. However, the results of August 2006 showed that the NH4 +-N concentrations of the summit soils were significantly higher than those of the footslope soils (P < 0.05), and that NO3 −-N concentrations in the open cores were significantly lower than those in the capped cores because of higher rainfall in the summer. In general, concentrations of mineral N and NO3 −-N in August were higher than those in January (both P = 0.0003), and NH4 +-N concentrations were significantly different between the different landscape positions (P < 0.05). There were larger soil C and N and microbial N pools at the summit position; however, footslope soils showed higher net N mineralization and nitrification rate as expressed on the basis of per unit C or N. Our results suggested that the substrate properties of the footslope position contributed to the higher net N mineralization and nitrification rate, and that the differences in N transformation rates between the landscape positions appeared to be related to vegetation type.

Sun/shade adaptations of the photosynthetic apparatus of Hoya carnosa, an epiphytic CAM vine, in a subtropical rain forest in northeastern Taiwan

Most past work on the ecophysiology of the Crassulacean acid metabolism (CAM) plant, Hoya carnosa, in the lab and in situ in Australia indicates that this epiphytic vine is better adapted to shaded, not exposed, locations, although a recent study of this species in Taiwan presents findings that run counter to this conclusion. Thus, photosynthetic characteristics of shaded and exposed individuals of H. carnosa were compared in situ in a subtropical rain forest in northeastern Taiwan in order to determine whether this CAM epiphyte is better adapted to the shade or the sun. Although leaves of shade plants had much greater chlorophyll concentrations than did those of sun plants, chlorophyll a/b ratios did not differ between the two groups of plants. Fluorescence measurements revealed some ability of leaves to acclimate to both shade and sun, although some evidence for photoinhibition (photoprotection) was observed in more exposed plants. Despite the latter, both exposed and shaded plants exhibited CAM, measured as diel fluctuations in leaf acidity, and CAM was more consistently found in the exposed plants. Furthermore, some evidence for more CAM at higher light availabilities was found. Overall, the results of this investigation reveal that H. carnosa in this subtropical rain forest in Taiwan exhibits adaptations to both high and low light levels, which should prove adaptive for an epiphytic vine with leaves on the same individual exposed to a wide range of exposure and shade in the host tree canopy.

Sporobolomyces magnisporus sp. nov., a new yeast species in the Erythrobasidium cluster isolated from plants in Taiwan.

Two strains of yeasts that contain Q-10 as the major ubiquinone, lack cellular xylose and produce large bilaterally symmetrical ballistoconidia were isolated from plants collected in a protected subtropical rain forest in Taiwan and were found to represent a new species. The taxonomic properties of this species coincide with the genus Sporobolomyces, so it is described as Sporobolomyces magnisporus sp. nov. In phylogenetic trees based on the nucleotide sequences of 18S ribosomal DNA and D1/D2 domain of 26S ribosomal DNA, this species is located in the Erythrobasidium cluster.

Throughfall Patterns in a Subtropical Rain Forest of Northeastern Taiwan

AbstractThroughfall chemistry of a subtropical rain forest in Taiwan was examined for 3 yr to understand patterns of nutrient inputs to the forests of this region. Annual throughfall fluxes for NH+4, NO−3, and SO2−4 (89, 28, and 83 mmol/m2/yr, respectively) were close to the levels of the most polluted areas in the temperate region. The lack of major emission sources near the study site indicates that most of the pollutants were regional and/or international in origin. High rates of cation leaching from the forest canopy were evident and the pattern is similar to that seen in heavily polluted temperate forests. Typhoons played a central role in the hydrology of the study forest with eight typhoons contributing 26% of the total rainfall in 320 h over the three years monitored. This typhoon input represented 20% of the total precipitation flux of the ions found in seasalt aerosols but less than 10% of anthropogenically enriched ions. Canopy leaching was an important source of base cations in throughfall and NO−3 was retained in the canopy. Using the Na‐ratio method the contribution of dry deposition relative to precipitation input was estimated to be 40% in the summer and 10% in the winter. The contribution of dry deposition to total deposition is small relative to many temperate forests and might result from the lack of long dry periods between precipitation events. Net throughfall flux was negatively related to precipitation concentration for H+, NH+4, NO−3, and SO2−4, suggesting that passive movement was important in characterizing throughfall dynamics.

Spatial Variability of Throughfall in a Subtropical Rain Forest in Taiwan

AbstractEight rainfalls were intensively sampled in a subtropical rain forest in northeastern Taiwan. This study, carried out at Fu‐shan Experimental Forest was designed to examine variability of throughfall characteristics. The volume and chemistry of the throughfall associated with individual rains have a high degree of spatial variability, with throughfall chemistry more variable than volume. When data from all of the storms were combined, there was lower variability than that seen with individual storms, largely as a result of a lack of consistent storm to storm spatial variation. Thus, individual storms cannot be used to represent the seasonal or annual pattern of spatial variation in throughfall chemistry or volume of the study forest. Twenty samples were required to estimate throughfall volume within 10% of the population mean with 95% confidence for individual storms. Yet, more than 100 samples were required to estimate the throughfall chemistry of some ions (e.g., H+). When the data from all eight storms were combined, 7, 20, and 25 samples were necessary to estimate throughfall volume, ion concentrations, and ion fluxes (except for Mg2+ and H+) within 10% of the population mean with 95% confidence. In the absence of estimates of spatial variation, differences in sampling protocols among throughfall studies make comparisons of throughfall characteristics difficult. In this study three funnels were used in tandem to capture small scale variability at each sample location, thus reducing spatial variability of throughfall chemistry.