天然林與杉木林不同冠層高度二氧化碳濃度的時間變化

Abstract

本研究目的為了解關刀溪天然闊葉林與人工杉木林於不同冠層高度二氧化碳濃度之分佈概況及垂直梯度的變化情形。採樣期間自2004年9月至2005年6月，於天然林與杉木林分別設置0.5 m、4 m、12 m及冠層外四個採樣高度，進行二氧化碳濃度的量測。結果顯示天然林與杉木林二氧化碳濃度分佈呈現梯度分層的現象，而其中以0.5 m處的二氧化碳濃度為最高，而12 m處與冠層外二採樣點的二氧化碳濃度，在季節與近一年的變化皆無顯著差異（P>0.05）。天然林0.5 m之各月份日間平均的二氧化碳濃度高於冠層外13.8~48.7 ppm，夜間則在10.8~59.4 ppm，日夜間濃度的差異後以6月份最大；杉木林0.5 m的各月份日間平均的二氧化碳濃度高於冠層外0~14.5 ppm，夜間則介於5.8~24.7 ppm，日夜間皆以9月有最大差值。天然林與杉木林之二氧化碳濃度在季節的變化上，各採樣點之日夜間二氧化碳濃度的差異以春季及夏季較大，秋冬季則略小。連續2天採取距地100 m之二氧化碳濃度的平均值約為379.6 ppm，全天均低於天然林12 m的二氧化碳濃度（約386.8 ppm），然與杉木林12 m的二氧化碳濃度差距小於1 ppm（約380.0 ppm），統計上並無顯著差異（P=0.78）。再者，天然林12 m處的二氧化碳濃度在日變化及近一年的變化均顯著受光照強度的影響較大；杉木林各採樣點二氧化碳濃度在日變化上受到光照強度之影響較大，而近一年的變化則受光照強度及溫度的交互影響。

The purpose of this study was to understand the variations of carbon dioxide concentration at different canopy heights on nature hardwood and China-fir plantation in GuanDauShi. The measurements were began in September 2004 and continued until the end of June 2005. There were four sampling heights, including 0.5, 4, 12 m and 2 m above canopy, at two stands, respectively. The results showed that a gradually increase in stratification of carbon dioxide concentration in nature hardwood and China-fir plantation. The highest concentration of carbon dioxide was found near the forest floor and the lowest ones at 12 m and 2 m above canopy, and the seasonal and yearly variations of sampling heights between 12 m and 2 m above canopy were not significant(P>0.05). The carbon dioxide concentration of 0.5 m at daytime in natural hardwood averagely was higher 13.8~48.7 ppm than 2 m above canopy and at night-time averagely was higher10.8~59.4 ppm than 2 m above canopy; The carbon dioxide concentration of 0.5 m at daytime in China-fir plantation averagely were higher 0~14.5 ppm than 2 m above canopy and at night-time averagely were higher 5.8~24.7 ppm than 2 m above canopy. The seasonal variations of carbon dioxide concentration between daytime and night-time of four sampling heights between daytime and night-time in Spring and Summer than in Winter. Carbon dioxide concentration of 100 m aboveground was 379.6 ppm averagely for two days on December, and was lower than the concentration of 12 m(386.8 ppm) in nature hardwood all day long. The variation of carbon dioxide concentration between 100 m aboveground and 12 m aboveground in China-fir plantation were very tiny(<1 ppm on average), and the differences weren't significant each other. On the other hand, the variations of carbon dioxide concentration of sampling height at 12 m in nature hardwood were influenced by light intensity, regardless of dialy or yearly variations. The dialy variation of carbon dioxide concentration for all sampling heights in China-fir plantation were influenced by light intensity, and the variations of the period about one year were influenced by light intensity and temperature.