Gas exchange of Populus euphratica leaves in a riparian zone

Riparian vegetation belts in arid regions of Central Asia are endangered to lose their ecosystem services due to intensified land use.For the development of sustained land use,management knowledge of plant performance in relation to resource supply is needed.We estimated productivity related functional traits at the edges of the habitat of Populus euphratica Oliv.Specific leaf area （SLA） and carbon/nitrogen （C/N） ratio of P.euphratica leaves growing near a former river bank and close to moving sand dunes in the Ebinur Lake National Nature Reserve in Xinjiang,Northwest China （near Kazakhstan） were determined and daily courses of CO2 net assimilation （PN）,transpiration （E）,and stomatal conductance （gs） of two consecutive seasons were measured during July-August 2007 and June-July 2008.Groundwater level was high （1.5-2.5 m below ground） throughout the years and no flooding occurred at the two tree stands.SLA was slightly lower near the desert than at the former river bank and leaves contained less N in relation to C.Highest E and gs of P.euphratica were reached in the morning before noon on both stands and a second low maximum occurred in the afternoon despite of the unchanged high levels of air to leaf water vapor pressure deficit （ALVPD）.Decline of gs in P.euphratica was followed by decrease of E.Water use efficiency （WUE） of leaves near the desert were higher in the morning and the evening,in contrast to leaves from the former river bank that maintained an almost stable level throughout the day.High light compensation points and high light saturation levels of PN indicated the characteristics of leaves well-adapted to intensive irradiation at both stands.In general,leaves of P.euphratica decreased their gs beyond 20 Pa/kPa ALVPD in order to limit water losses.Decrease of E did not occur in both stands until 40 Pa/kPa ALVPD was reached.Full stomatal closure of P.euphratica was achieved at 60 Pa/kPa ALVPD in both stands.E through the leaf surface amounted up to 30％ of the highest E rates,indicating dependence on water recharge from the ground despite of obviously closed stomata.A distinct leaf surface temperature （Tleaf） threshold of around 30℃ also existed before stomata started to close.Generally,the differences in gas exchange between both stands were small,which led to the conclusion that micro-climatic constraints to E and photosynthesis were not the major factors for declining tree density with increasing distance from the river.

“干清粪”系统猪粪快速堆肥过程中添加剂对甲烷、氧化亚氮和氨气排放的影响(英文)

研究目的:在"干清粪"系统猪粪堆肥过程中,不同添加剂(玉米秸秆、锯末和蘑菇渣)处理对甲烷、氧化亚氮和氨气排放的影响。创新要点:将不同的添加剂(玉米秸秆、锯末和蘑菇渣)应用到快速堆肥系统中进行堆肥,测定了猪粪堆肥过程中甲烷、氧化亚氮和氨气的排放规律,为国内猪粪堆肥的应用提供理论指导。重要结论:玉米秸秆作为添加剂能增加猪粪堆肥过程中氧化亚氮的排放;蘑菇渣添加剂增加了堆肥过程中甲烷的排放,然而减少了氧化亚氮及氨气的排放;锯末处理能增加堆肥过程中氨气的排放。添加剂能显著影响堆肥过程中氮素的损失。

Effect of phosphogypsum and dicyandiamide as additives on NH_3,N_2O and CH_4 emissions during composting

A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide （DCD, C2 H4 N4 ） as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N20 emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N20 emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3 , CH4 and N20 emissions.0ptimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study.

Effects of aeration method and aeration rate on greenhouse gas emissions during composting of pig feces in pilot scale

The aim of this study was to uncover ways to mitigate greenhouse gas（GHG） emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates（0, 0.18, 0.36, and 0.54 L/（kg dry matter（dm）·min）） and methods（continuous and intermittent） on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7：1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses,but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration,the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2 O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2 O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days.