Humic Acid Composition and Characteristics of Soil Organic Matter in Relation to the Elevation Gradient of Moso Bamboo Plantations.

Studying the influence of climatic and/or site-specific factors on soil organic matter (SOM) along an elevation gradient is important for understanding the response of SOM to global warming. We evaluated the composition of SOM and structure of humic acids along an altitudinal gradient from 600 to 1400 m in moso bamboo (Phyllostachys edulis) plantations in central Taiwan using NMR spectroscopy and photometric analysis. Total organic C and total nitrogen (N) content increased with increasing elevation. Aromaticity decreased and ΔlogK (the logarithm of the absorbance ratio of humic acids at 400 and 600 nm) increased with increasing elevation, which suggests that SOM humification decreased with increasing elevation. High temperature at low elevations seemed to enhance the decomposition (less accumulation of total organic C and N) and humification (high aromaticity and low ΔlogK). The alkyl-C/O-alkyl-C (A/O-A) ratio of humic acids increased with increasing elevation, which suggests that SOM humification increased with increasing elevation; this finding was contrary to the trend observed for ΔlogK and aromaticity. Such a discrepancy might be due to the relatively greater remaining of SOM derived from high alkyl-C broadleaf litter of previous forest at high elevations. The ratio of recalcitrant C to total organic C was low at low elevations, possibly because of enhanced decomposition of recalcitrant SOM from the previous broadleaf forest during long-term intensive cultivation and high temperature. Overall, the change in SOM pools and in the rate of humification with elevation was primarily affected by changes in climatic conditions along the elevation gradient in these bamboo plantations. However, when the composition of SOM, as assessed by NMR spectroscopy and photometric analysis was considered, site-specific factors such as residual SOM from previous forest and intensive cultivation history could also have an important effect on the humic acid composition and humification of SOM.

Plant bioclimatic models in climate change research.

Bioclimatics is an ancient science that was once neglected by many ecologists. However, as climate changes have attracted increasing attention, scientists have reevaluated the relevance of bioclimatology and it has thus become essential for exploring climate changes. Because of the rapidly growing importance of bioclimatic models in climate change studies, we evaluated factors that influence plant bioclimatology, constructed and developed bioclimatic models, and assessed the precautionary effects of the application of the models. The findings obtained by sequentially reviewing the development history and importance of bioclimatic models in climate change studies can be used to enhance the knowledge of bioclimatic models and strengthen their ability to apply them. Consequently, bioclimatic models can be used as a powerful tool and reference in decision-making responses to future climate changes. The objectives of this study were to (1) understand how climatic factors affect plants; (2) describe the sources, construction principles, and development of early plant bioclimatic models (PBMs); and (3) summarize the recent applications of PBMs in climate change research.

Forest cover reduces thermally suitable habitats and affects responses to a warmer climate predicted in a high-elevation lizard.

Warmer climates have affected animal distribution ranges, but how they may interact with vegetation patterns to affect habitat use, an important consideration for future wildlife management, has received little attention. Here, we use a biophysical model to investigate the potential thermal impact of vegetation pattern on the habitat quality of a high-elevation grassland lizard, Takydromus hsuehshanensis, and to predict the thermal suitability of vegetation for this species in a future warmer climate (assuming 3 °C air temperature increase). We assess the thermal quality of vegetation types in our study area (Taroko National Park in areas >1,800 m) using three ecologically relevant estimates of reptiles: body temperature (T b), maximum active time, and maximum digestive time. The results show that increasing forest canopy gradually cools the microclimates, hence decreasing these estimates. In the current landscape, sunny mountain-top grasslands are predicted to serve as high quality thermal habitat, whereas the dense forests that are dominant as a result of forest protection are too cold to provide suitable habitat. In simulated warmer climates, the thermal quality of dense forests increases slightly but remains inferior to that of grasslands. We note that the impact of warmer climates on this reptile will be greatly affected by future vegetation patterns, and we suggest that the current trend of upslope forest movement found in many other mountain systems could cause disadvantages to some heliothermic lizard species.