Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon d...Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon dioxide concentration and thus of water-use efficiency (WUE) in plants, were measured on Leymus chinensis (Trin.) Tzvel. and Cleistogenes squarrosa (Trin.) Keng. in six communities of different habitats in die Xilin River Basin. The foliar delta C-13 values of both species tended to increase with decreasing soil water content (SWC) and a significant negative correlation was found between foliar delta C-13 Values and SWC in different soil layers, indicating that the two species could change WUE according to water availability. We also found relatively constant leaf water contents (LWC) of the two species in different habitats. Our results implied that the two steppe species might have adapted to different soil water regimes either through adjusting stomatal conductance to get a proper WUE, or through enhancing the osmosis-regulating ability to keep a relatively stable LWC. Our findings could partially explain why the two plant species have a wide distribution range and become dominant in the Xilin River Basin.展开更多
Effects of nutrients(compounds of macro-and micro-elements)supply without sulfur(T_(1))and with sulfur(T_(2))on the competition between Stipa grandis L.(C_(3) )and Cleistogenes squarrosa L.(C_(4) )were examined using ...Effects of nutrients(compounds of macro-and micro-elements)supply without sulfur(T_(1))and with sulfur(T_(2))on the competition between Stipa grandis L.(C_(3) )and Cleistogenes squarrosa L.(C_(4) )were examined using a replacement series design in a greenhouse experiment over a period of 80 d.Blank treatment(nothing applied)(To)was conducted simultaneously.it seems to be no inter-competition between S.grandis and C.squarrosa in all treatments.There was also no intra-competition for S.grandis in all treatments,and for C.squarrosa under T0 treatment because of low productivity.However,the intra-competition of aboveground of C squarrosa was significant when nutrients were supplied regardless of sulfur(S)application.The interaction on dry weight of C.squarrosa per pot between S supply and proportion of C.squarrosa was observed.Under the treatments of T_(1)and T_(2)the shoot growth of S.grandis increased significantly compared with To treatment,but there was no significant difference between T_(1)and T_(2)treatments,indicating S had no effect on it.Root morphologies of S.grandis was not sensitive to nutrients added.Nutrients supply(T_(1)and T_(2)treatments)not only increased significantly the shoot growth of C.squarrosa,but also increased significantly its root growth.Sulfur increased significantly growth of the shoot and root of C.squarrosa.Nutrients supply decreased significantly ratio of root to shoot dry matter(RRS)of C.squarrosa regardless of S application,but the RRS of S.grandis was not affected by nutrients applied.Sulfur also decreased significantly the RRS of C.squarrosa in 100%and 75%proportions of C.squarrosa.The RRS of C.squarrosa was greater significantly in the 100%proportion than that in the 25%proportion of C.squarrosa for all treatments.Therefore,photosynthesis is more allocated to root in infertility soils than in fertility soils and the competition for nutrient resources stimulates root production.The degree of leaf greenness of C.squarrosa in T_(1)treatment was less significantly than that in To and T_(2)treatments,and it was greater significantly in the 25%proportion than in the 100%proportion of C.squarrosa under T_(1)and T_(2)treatments,indicating that nutrients supply increase chlorophyll content in plant and may accentuate S deficiency or low plant productivity alleviate S deficiency.展开更多
文摘Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon dioxide concentration and thus of water-use efficiency (WUE) in plants, were measured on Leymus chinensis (Trin.) Tzvel. and Cleistogenes squarrosa (Trin.) Keng. in six communities of different habitats in die Xilin River Basin. The foliar delta C-13 values of both species tended to increase with decreasing soil water content (SWC) and a significant negative correlation was found between foliar delta C-13 Values and SWC in different soil layers, indicating that the two species could change WUE according to water availability. We also found relatively constant leaf water contents (LWC) of the two species in different habitats. Our results implied that the two steppe species might have adapted to different soil water regimes either through adjusting stomatal conductance to get a proper WUE, or through enhancing the osmosis-regulating ability to keep a relatively stable LWC. Our findings could partially explain why the two plant species have a wide distribution range and become dominant in the Xilin River Basin.
文摘Effects of nutrients(compounds of macro-and micro-elements)supply without sulfur(T_(1))and with sulfur(T_(2))on the competition between Stipa grandis L.(C_(3) )and Cleistogenes squarrosa L.(C_(4) )were examined using a replacement series design in a greenhouse experiment over a period of 80 d.Blank treatment(nothing applied)(To)was conducted simultaneously.it seems to be no inter-competition between S.grandis and C.squarrosa in all treatments.There was also no intra-competition for S.grandis in all treatments,and for C.squarrosa under T0 treatment because of low productivity.However,the intra-competition of aboveground of C squarrosa was significant when nutrients were supplied regardless of sulfur(S)application.The interaction on dry weight of C.squarrosa per pot between S supply and proportion of C.squarrosa was observed.Under the treatments of T_(1)and T_(2)the shoot growth of S.grandis increased significantly compared with To treatment,but there was no significant difference between T_(1)and T_(2)treatments,indicating S had no effect on it.Root morphologies of S.grandis was not sensitive to nutrients added.Nutrients supply(T_(1)and T_(2)treatments)not only increased significantly the shoot growth of C.squarrosa,but also increased significantly its root growth.Sulfur increased significantly growth of the shoot and root of C.squarrosa.Nutrients supply decreased significantly ratio of root to shoot dry matter(RRS)of C.squarrosa regardless of S application,but the RRS of S.grandis was not affected by nutrients applied.Sulfur also decreased significantly the RRS of C.squarrosa in 100%and 75%proportions of C.squarrosa.The RRS of C.squarrosa was greater significantly in the 100%proportion than that in the 25%proportion of C.squarrosa for all treatments.Therefore,photosynthesis is more allocated to root in infertility soils than in fertility soils and the competition for nutrient resources stimulates root production.The degree of leaf greenness of C.squarrosa in T_(1)treatment was less significantly than that in To and T_(2)treatments,and it was greater significantly in the 25%proportion than in the 100%proportion of C.squarrosa under T_(1)and T_(2)treatments,indicating that nutrients supply increase chlorophyll content in plant and may accentuate S deficiency or low plant productivity alleviate S deficiency.
