The effects of water, nitrogen and phosphorus on productivity of sandy grassland were investigated with a fully factorial experi- ment to find out the main factors limiting natural restoration of grassland productivit...The effects of water, nitrogen and phosphorus on productivity of sandy grassland were investigated with a fully factorial experi- ment to find out the main factors limiting natural restoration of grassland productivity in the southeastern Keerqin sandy land. In total, eight treatments were designed as water addition （W）, nitrogen fertilizer addition （N）, phosphorus fertilizer addition （P）, water ＋ nitrogen fertilizer addition （WN）, water ＋ phosphorus fertilizer addition （WP）, nitrogen fertilizer ＋ phosphorus fertilizer addition （NP）, water ＋ nitrogen fertilizer ＋ phosphorus fertilizer addition （WNP） and control （CK）. Each treatment was replicated six times and randomly assigned to 48 plots （4 m × 4 m） that were separated by a 2-m buffer. Results show that restoration of productivity is only limited by nitrogen factor for sandy grassland of Keerqin sandy land and not limited by water and phosphorus. Relative to CK plots, the biomass and the aboveground net primary productivity （ANPP） of all the plots added with nitrogen fertilizer were significantly enhanced （P 〈 0.05） in 2005 growing season. Grass root mass is dominant in underground biomass. The present study possibly underestimates net primary productivity of grassland in northern China, due to limitation of underground biomass measurements.展开更多
Keerqin sand land is located in the transitional terrain between the Northeast Plain and Inner Mongolia （42°41′-45°15′N, 118°35′-123°30′ E） in Northeast China and it is seriously affected by ...Keerqin sand land is located in the transitional terrain between the Northeast Plain and Inner Mongolia （42°41′-45°15′N, 118°35′-123°30′ E） in Northeast China and it is seriously affected by desertification. According to the configuration and ecotope of the earths surface, the coverage of vegetation, occupation ratio of bare sandy land and the soil texture were selected as evaluation indexes by using the field investigation data. The evaluation index system of Keerqin sandy desertification was established by using Remote Sensing data. and the occupation ratio of bare sandy land was obtained by mixed spectrum model. This index system is validated by the field investioation data and results indicate that it is suitable for the desertification evaluation of Keerqin.Foundation Item： This study is supported by a grant from the National Natural Science Foundation of China （No. 30371192）展开更多
Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in ...Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.展开更多
Nitrogen was the main limiting nutrient of net primary production in the southeastern Keerqin Sandy Lands, Northeast China. Species richness declined and biomass increased after five consecutive years of nitrogen fert...Nitrogen was the main limiting nutrient of net primary production in the southeastern Keerqin Sandy Lands, Northeast China. Species richness declined and biomass increased after five consecutive years of nitrogen fertilization of these sandy grasslands （2004-2008）. After fertilization had been stopped for three years （2009-2011）, we surveyed vegetation on previously fertilized plots to quantify changes in commu- nity composition. Respect species richness showed an increasing trend over time since the cessation of fertilization. Respect vegetation height and coverage showed decreasing trends over time since the cessation of fertilization. Species composition changed after fertilization ceased, the dominant species shifting from Cannabis sativa, Phragmites communis and Chenopodium acuminaturn in 2008 to Cannabis sativa, Phragmites communis and Artemisia scoparia in 2011. Dominance of dominant species declined from 66.2% in 2008 to 57.5% in 2011. The importance value of annual plants in the earlier nitrogen addition plots was higher than in control plots, but the differences were not significant in 2011. The importance value of perennial plants differed significantly between treatments from 2009 to 2011. The reversion rate not only differed be- tween community characteristics, but also between functional groups in the same community characteristic. Although the residual effect of nitrogen addition on vegetation was still observed three years after fertilization ceased, the vegetation showed signs of recovery.展开更多
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX1-YW-08-02-02)the National Basic Research Program of China (2007CB106803)+1 种基金the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period (2006BAC01A122006BAD26B0201-1)
文摘The effects of water, nitrogen and phosphorus on productivity of sandy grassland were investigated with a fully factorial experi- ment to find out the main factors limiting natural restoration of grassland productivity in the southeastern Keerqin sandy land. In total, eight treatments were designed as water addition （W）, nitrogen fertilizer addition （N）, phosphorus fertilizer addition （P）, water ＋ nitrogen fertilizer addition （WN）, water ＋ phosphorus fertilizer addition （WP）, nitrogen fertilizer ＋ phosphorus fertilizer addition （NP）, water ＋ nitrogen fertilizer ＋ phosphorus fertilizer addition （WNP） and control （CK）. Each treatment was replicated six times and randomly assigned to 48 plots （4 m × 4 m） that were separated by a 2-m buffer. Results show that restoration of productivity is only limited by nitrogen factor for sandy grassland of Keerqin sandy land and not limited by water and phosphorus. Relative to CK plots, the biomass and the aboveground net primary productivity （ANPP） of all the plots added with nitrogen fertilizer were significantly enhanced （P 〈 0.05） in 2005 growing season. Grass root mass is dominant in underground biomass. The present study possibly underestimates net primary productivity of grassland in northern China, due to limitation of underground biomass measurements.
基金This study is supported by a grant from the National Natural Science Foundation of China （No. 30371192）
文摘Keerqin sand land is located in the transitional terrain between the Northeast Plain and Inner Mongolia （42°41′-45°15′N, 118°35′-123°30′ E） in Northeast China and it is seriously affected by desertification. According to the configuration and ecotope of the earths surface, the coverage of vegetation, occupation ratio of bare sandy land and the soil texture were selected as evaluation indexes by using the field investigation data. The evaluation index system of Keerqin sandy desertification was established by using Remote Sensing data. and the occupation ratio of bare sandy land was obtained by mixed spectrum model. This index system is validated by the field investioation data and results indicate that it is suitable for the desertification evaluation of Keerqin.Foundation Item： This study is supported by a grant from the National Natural Science Foundation of China （No. 30371192）
基金This paper is supported by the Key Laboratory of Ter-restrial Ecological Process and Regional Ecological Safety in Liaoning Province (06ZDS212SS)the Knowledge Innovation Program of the Chinese Academy of Sciences (07SBS115S3).
文摘Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.
基金supported by the Chinese Academy of Sciences,Projects No.XDA05050401 and XDA050570100the National Natural Science Foundation of China,Project No.30800143
文摘Nitrogen was the main limiting nutrient of net primary production in the southeastern Keerqin Sandy Lands, Northeast China. Species richness declined and biomass increased after five consecutive years of nitrogen fertilization of these sandy grasslands （2004-2008）. After fertilization had been stopped for three years （2009-2011）, we surveyed vegetation on previously fertilized plots to quantify changes in commu- nity composition. Respect species richness showed an increasing trend over time since the cessation of fertilization. Respect vegetation height and coverage showed decreasing trends over time since the cessation of fertilization. Species composition changed after fertilization ceased, the dominant species shifting from Cannabis sativa, Phragmites communis and Chenopodium acuminaturn in 2008 to Cannabis sativa, Phragmites communis and Artemisia scoparia in 2011. Dominance of dominant species declined from 66.2% in 2008 to 57.5% in 2011. The importance value of annual plants in the earlier nitrogen addition plots was higher than in control plots, but the differences were not significant in 2011. The importance value of perennial plants differed significantly between treatments from 2009 to 2011. The reversion rate not only differed be- tween community characteristics, but also between functional groups in the same community characteristic. Although the residual effect of nitrogen addition on vegetation was still observed three years after fertilization ceased, the vegetation showed signs of recovery.
