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Response of aboveground biomass and diversity to nitrogen addition along a degradation gradient in the Inner Mongolian steppe, China.

Xu X, Liu H, Song Z, Wang W, Hu G, Qi Z - Sci Rep (2015)

Bottom Line: Fields with a higher level of degradation tended to have a higher saturation value (20 g N m(-2) yr(-1)) than those with a lower degradation level ( < 10 g N m(-2) yr(-1)).After three years of experimentation, species richness showed little change across degradation levels.Among the four functional groups of grasses, sedges, forbs and legumes, grasses shared the most similar response patterns with those of the whole community, demonstrating the predominant role that they play in the restoration of grassland under a stimulus of nitrogen addition.

View Article: PubMed Central - PubMed

Affiliation: College of Urban and Environmental Sciences and MOE Laboratory for Earth Surface Processes, Peking University, Beijing, 100871, China.

ABSTRACT
Although nitrogen addition and recovery from degradation can both promote production of grassland biomass, these two factors have rarely been investigated in combination. In this study, we established a field experiment with six N-treatment (CK, 10, 20, 30, 40, 50 g N m(-2) yr(-1)) on five fields with different degradation levels in the Inner Mongolian steppe of China from 2011-2013. Our observations showed that while the external nitrogen increased the aboveground biomass in all five grasslands, the magnitude of the effects differed with the severity of degradation. Fields with a higher level of degradation tended to have a higher saturation value (20 g N m(-2) yr(-1)) than those with a lower degradation level ( < 10 g N m(-2) yr(-1)). After three years of experimentation, species richness showed little change across degradation levels. Among the four functional groups of grasses, sedges, forbs and legumes, grasses shared the most similar response patterns with those of the whole community, demonstrating the predominant role that they play in the restoration of grassland under a stimulus of nitrogen addition.

No MeSH data available.


The proportion of each experimental field of three groups categorized to indicate the level of degradation in this region: pioneer species (annual, in black), intermediate species (degradation indicators, in dark grey), and climax species (in light grey). The X axis represents the degradation levels of the five fields from high to low.
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f5: The proportion of each experimental field of three groups categorized to indicate the level of degradation in this region: pioneer species (annual, in black), intermediate species (degradation indicators, in dark grey), and climax species (in light grey). The X axis represents the degradation levels of the five fields from high to low.

Mentions: Our experiment was conducted on the Ulan Buton steppe, Inner Mongolian Plateau, China. The study area is characterized by a mean annual precipitation of around 400 mm and a mean annual temperature of –1.4°C. The soil is classified as Chernozems, with sand and silt dominating its surface layer50. Particle size data are shown in Table 1. Five 100 m × 100 m experimental fields were fenced at the flat land surface in the spring of 2011 after communicating with local people about the history of human disturbances at each site. Among all vegetation and soil features, plant species composition and community structure can indicate the status of grassland degradation well. In previous studies, the herb species of grassland in this region could be categorized into three groups: annuals (mainly appearing in the seriously degraded steppe), moderate grazing degradation indicators, and climax species in mature steppe50. To quantify the grassland degradation level, we classified each site as being in one of five stages according to the proportion of the three groups of species. For example, AF had the highest proportion of annuals among the five fields and MG had the highest proportion of climax species, while the proportion of moderately grazing degradation indicators was high in the other three. The following relative covers (ranging from 0 to 1) of climax species of degraded and climax grassland, which could indicate the gradient well, were observed: abandoned farmland (AF, with 0.26), extremely degraded grassland (ED, with 0.34), severely degraded grassland (SD, with 0.40), moderately degraded grassland (MD, with 0.54), and mature grassland (MG, with 0.74) (Table 1, Fig. 5)50. This degradation sequence was mainly based on the meaning of the species composition degradation, but could also be adopted as a surrogate of the extent of human disturbance. At one end of the sequence is the abandoned farmland, which is heavily managed grassland at the pioneer stage of secondary succession. At the other end of the sequence is mature grassland with slight or no human disturbance.


Response of aboveground biomass and diversity to nitrogen addition along a degradation gradient in the Inner Mongolian steppe, China.

Xu X, Liu H, Song Z, Wang W, Hu G, Qi Z - Sci Rep (2015)

The proportion of each experimental field of three groups categorized to indicate the level of degradation in this region: pioneer species (annual, in black), intermediate species (degradation indicators, in dark grey), and climax species (in light grey). The X axis represents the degradation levels of the five fields from high to low.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508527&req=5

f5: The proportion of each experimental field of three groups categorized to indicate the level of degradation in this region: pioneer species (annual, in black), intermediate species (degradation indicators, in dark grey), and climax species (in light grey). The X axis represents the degradation levels of the five fields from high to low.
Mentions: Our experiment was conducted on the Ulan Buton steppe, Inner Mongolian Plateau, China. The study area is characterized by a mean annual precipitation of around 400 mm and a mean annual temperature of –1.4°C. The soil is classified as Chernozems, with sand and silt dominating its surface layer50. Particle size data are shown in Table 1. Five 100 m × 100 m experimental fields were fenced at the flat land surface in the spring of 2011 after communicating with local people about the history of human disturbances at each site. Among all vegetation and soil features, plant species composition and community structure can indicate the status of grassland degradation well. In previous studies, the herb species of grassland in this region could be categorized into three groups: annuals (mainly appearing in the seriously degraded steppe), moderate grazing degradation indicators, and climax species in mature steppe50. To quantify the grassland degradation level, we classified each site as being in one of five stages according to the proportion of the three groups of species. For example, AF had the highest proportion of annuals among the five fields and MG had the highest proportion of climax species, while the proportion of moderately grazing degradation indicators was high in the other three. The following relative covers (ranging from 0 to 1) of climax species of degraded and climax grassland, which could indicate the gradient well, were observed: abandoned farmland (AF, with 0.26), extremely degraded grassland (ED, with 0.34), severely degraded grassland (SD, with 0.40), moderately degraded grassland (MD, with 0.54), and mature grassland (MG, with 0.74) (Table 1, Fig. 5)50. This degradation sequence was mainly based on the meaning of the species composition degradation, but could also be adopted as a surrogate of the extent of human disturbance. At one end of the sequence is the abandoned farmland, which is heavily managed grassland at the pioneer stage of secondary succession. At the other end of the sequence is mature grassland with slight or no human disturbance.

Bottom Line: Fields with a higher level of degradation tended to have a higher saturation value (20 g N m(-2) yr(-1)) than those with a lower degradation level ( < 10 g N m(-2) yr(-1)).After three years of experimentation, species richness showed little change across degradation levels.Among the four functional groups of grasses, sedges, forbs and legumes, grasses shared the most similar response patterns with those of the whole community, demonstrating the predominant role that they play in the restoration of grassland under a stimulus of nitrogen addition.

View Article: PubMed Central - PubMed

Affiliation: College of Urban and Environmental Sciences and MOE Laboratory for Earth Surface Processes, Peking University, Beijing, 100871, China.

ABSTRACT
Although nitrogen addition and recovery from degradation can both promote production of grassland biomass, these two factors have rarely been investigated in combination. In this study, we established a field experiment with six N-treatment (CK, 10, 20, 30, 40, 50 g N m(-2) yr(-1)) on five fields with different degradation levels in the Inner Mongolian steppe of China from 2011-2013. Our observations showed that while the external nitrogen increased the aboveground biomass in all five grasslands, the magnitude of the effects differed with the severity of degradation. Fields with a higher level of degradation tended to have a higher saturation value (20 g N m(-2) yr(-1)) than those with a lower degradation level ( < 10 g N m(-2) yr(-1)). After three years of experimentation, species richness showed little change across degradation levels. Among the four functional groups of grasses, sedges, forbs and legumes, grasses shared the most similar response patterns with those of the whole community, demonstrating the predominant role that they play in the restoration of grassland under a stimulus of nitrogen addition.

No MeSH data available.