The effects of forest and snow cover on the water and chemical cycles in cold snowy watersheds

森林和积雪对冷雪流域水和化学循环的影响

基本信息

批准号：
11490001
负责人：
ISHIKAWA Nobuyoshi
金额：
$ 4.61万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2002
项目状态：
已结题

项目摘要

For understanding the effects of forest and snow cover on the water, CO_2 and chemical cycles were examined at two different experimental watersheds from 1999 to 2003 including three snow cover seasons. One watershed located at the northern part of Hokkaido where the annual temperature range was -30℃ to 25℃ and the maximum snow depth was more than 2m. The other was at the southern part of Hokkaido, where the temperature range was -25℃ to 25℃ and the snow depth was below 50cm. Vegetations of both sites are mixed forests of evergreen needle leaf trees and deciduous broad-leaved trees with bamboo bush undergrowth. Observation items are radiative heat flux, turbulent heat flux, evapo-transpiration, CO_2 concentration above canopy and forest floor, chemical contents of river water, snowmelt water, groundwater and precipitation.The main observational results are : 【○!1】Evapo-transpiration above canopy showed remarkable seasonal variation and even in mid-summer it occupied 30-40% of the net radiation , which was smaller compared with other reports. 【○!2】The absorbed CO_2 by broad-leaved forest was 2680-2200kgC/ha/yr, which qualitatively consists with the growth rates of trees. Soil respiration was 4100-3900kg/C/ha/yr and showed daily and seasonal variations according to the change of soil temperature. 【○!3】CO_2 concentration at the bottm of snow cover in mid-winter sometime exceeded 1200ppm. CO_2 in the atmosphere just above the snow cover showed no daily variation in the mid-winter but clear daily variation appeared after March. 【○!4】During snow melting season the runoff ratio of water was 80-85%, however the chemical balance showed that the outflow of iron exceeded more than two times of the inflow, which suggested the inflow of snow-free season reserved in the watershed for a while and drained in the snowmelt season.

为了了解森林和雪覆盖对水的影响，在1999年至2003年的两个不同的实验流域中检查了CO_2和化学周期，包括三个雪覆盖季节。一个分水岭位于北海道北部，年温度范围为-30℃至25°，最大的雪深度超过2m。另一个在北海道的南部，温度范围为-25℃至25°，雪深度低于50厘米。这两个地点的植被都是常绿针叶的混合森林，并决定宽叶树的叶子，上面有竹灌木。观察项目是辐射热通量，湍流的热量，蒸发流动性，CO_2浓度高于树冠和森林地板上方，河水的化学含量，河水融化水，地下水和降水的主要观察结果是：[[○○！1]蒸发量的季节性变化较大的季节性变化和较较大的季度的散布范围，其较小的是在30％的情况下，它的其他30％的降级为30％。 [○！2]阔叶森林吸收的CO_2为2680-2200kgc/ha/yr，质量上是树木的生长速率。土壤呼吸为4100-3900kg/c/ha/yr，根据土壤温度的变化，每天和季节性变化。 [○！3]冬季雪盖底部的CO_2浓度有时超过1200ppm。 CO_2在雪覆盖上方的大气中，冬季中期没有每天的变化，但每天在3月之后出现清晰的变化。 [○！4]在雪融化季节，水的径流比为80-85％，但是化学平衡表明，铁的出口超过两次，这表明在流域中保留了一段时间的无雪季节流入，并在雪地季节中排出。