%0 Journal Article
%T Measurement and Analysis of Water, Heat and CO2 Flux from a Farmland in the North China Plain<br>华北平原典型农田水、热与CO2通量的测定
%A ZHANG Yongqiang
%A SHEN Yanjun
%A LIU Changming
%A Yu Qiang
%A SUN Hongyong
%A JIA Jinsheng
%A TANG ChangyUan
%A AKIHIKO Kondohl
%A <br>张永强
%A 沈彦俊
%A 刘昌明
%A 于强
%A 孙宏勇
%A 贾金生
%A 唐常源
%A A.Kondoh
%J 地理学报
%D 2002
%I 
%X Surface energy fluxes including net radiation (Rn), latent heat flux (λE), sensible heat flux (H), soil heat flux (G) and carbon dioxide flux (FCO2) were measured by Bowen-ratio energy balance technique and eddy correlation technique from a farmland at Luancheng Agro-ecosystem Station, Chinese Academy of Sciences in the North China Plain from 1999 to 2001. Seasonal variation of a ratio of latent heat flux (λE) divided by net radiation flux (Rn) showed that Rn is mainly used to evapotranspirate by crops. λE/Rn was all higher than 70% during the four observed seasons in the two years. λE/Rn above maize canopy is slightly higher than that above winter wheat canopy. Seasonal average ratio of sensible heat flux (H) divided by Rn keeps about 15% above the field surface; seasonal average ratio of conductive heat flux (G) divided by Rn varies between 5% and 13%, and the average G/Rn from wheat canopy is evidently higher than that from maize canopy. Under given environmental conditions, when the available energy (Rn-G) is less than 200 W/m2, evaporative fraction (EF) decreases sharply; below Rn-G≈200 W/m2, EF decreases gradually until stabilizing at some specific value less than 1.0. The response process of EF to Rn-G under winter wheat field conditions is similar to that under the given conditions. With the increase of photosynthesis photo flux density (PPFD), carbon dioxide flux (FCO2) changes according to the curve of Michaelis-Mente. Water use efficiency (WUE) does not show the maximum when PPFD is the maximum at noon. On the contrary, WUE gradually decreased with PPFD equal to 1500 μmol m-2 s-1.
%K 农田水
%K 感热通量
%K 潜热通量
%K CO2通量
%K 水分利用效率
%K 华北平原
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=869B153A4C6B5B85&jid=F7B5B947C24B9D649491012214E4BEF4&aid=7902691B4366B6E3&yid=C3ACC247184A22C1&vid=11B4E5CC8CDD3201&iid=38B194292C032A66&sid=B66C5792F4740920&eid=A04F01817ECB9A48&journal_id=0375-5444&journal_name=地理学报&referenced_num=36&reference_num=37