Sap Flow of Abies georgei var. smithii and Its Relationship with the Environment Factors in the Tibetan Subalpine Region, China

Abies georgei var. smithii is a dominant species playing an important role in protecting biodiversity and sustaining the forestry ecosystems in Southeastern Tibetan Plateau. Stem sap flows of five different diameters at the breast height(DBH) A. georgei var. smithii samples were monitored continuously with the thermal dissipation probe for the entire growing period in order to understand the water transportation mechanism and the effects of environmental factors on its transpiration and growth. Relative environment factors, temperature and humidity of air, photosynthetically active radiation, rainfall, and wind speed, soil moisture, etc. were measured by the automatic weather stations. Diurnal and seasonal variations in sap flow rate with the different stem diameters and their correlations with meteorological factors were analyzed. The diurnal change in sap flow velocity showed a single-peak curve at the daily time scale, whereas a lower sap flow velocity can be observed in the largest DBH sample tree at night. The maximum average velocity was observed in August, whereas the minimum velocity was observed in January, and a large amount of water evaporated in summer owing to the higher sap flow velocity. In addition, sap flow velocity was closely related to changes in the micrometeorological factors, with average sap flow velocity showing significant linear correlations with air temperature, photosynthetically active radiation, rainfall, and vapor pressure deficit of air and soil moisture. Therefore, some measures, improving the light and temperature conditions, should be taken for protecting A. georgei var. smithii population in the Tibetan Plateau.

Susceptible conditions for debarking by deer in subalpine coniferous forests in central Japan

Background： Recently, deer have expanded their distribution to higher altitude ranges including subalpine forests However, culling deer and construction of deer fence in subalpine forests are difficult because of steep slopes and complex topography. Thus it is necessary to clarify the factors which are associated with debarking by deer for the effective protection of subalpine forests. In this study, we examined which factors are associated with debarking b： sika deer （Cervus nippon） in subalpine coniferous forests. Methods： We conducted our survey in Minami-Alps National Park, central Japan. We established 24 10 m × 40 m plots and surveyed the occurrence of debarking on saplings 〉30 cm in height and 〈3 cm in diameter at breast heigh （DBH） and on trees 〉3 cm in DBH, as well as sapling density within each plot. Minimum distances to nearest grasslan（ of plots were calculated （tentatively assuming grassland would attract deer and would cause high debarking pressure in the surrounding subaipine forests）. Results： The mean percentage of debarked live saplings was higher than that of live trees. The mean percentage of debarked saplings which had already died was 81.6 %. Debarking of saplings increased with lower elevation taller sapling size, and marginally increased near grassland. Sapling density was lower in plots with low basa area of conspecific trees near grassland and differed among species. Sapling density marginally decreased with decreasing elevation and increasing stand tree density. Debarking of trees was positively related to small DBH and Io~ elevation, and marginally increased near grassland and differed among species. Conclusions： Our results suggest that tall saplings in subalpine forests of low elevation or near subalpine grassland were susceptible to debarking by deer and monitoring of these areas may permit the early detection of the impacts of deer in subalpine coniferous forests.