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Leaf meristems: an easily ignored component of the response to human disturbance in alpine grasslands.

Hong J, Ma X, Wang X - Ecol Evol (2016)

Bottom Line: The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels.The R/S and M b/M a should be cautiously used in combination in the future research.The understanding of the distinction between the R-S and M b-M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China; University of Chinese Academy of SciencesBeijing100049China.

ABSTRACT
Grazing and fencing are two important factors that influence productivity and biomass allocation in alpine grasslands. The relationship between root (R) and shoot (S) biomass and the root:shoot ratio (R/S) are critical parameters for estimating the terrestrial carbon stocks and biomass allocation mechanism responses to human activities. Previous studies have often used the belowground:aboveground biomass ratio (M b/M a) to replace the R/S in alpine ecosystems. However, these studies may have neglected the leaf meristem biomass, which belongs to the shoot but occurs below the soil surface, leading to a significant overestimation of the R/S ratio. We conducted a comparative study to explore the differences between the R/S and M b/M a at both the species (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) and community levels on a Tibetan alpine grassland with grazing and fencing management blocks. The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels. For S. purpurea, the M b/M a was three times higher than the R/S. The M b/M a was approximately two times higher than the R/S for the species of C. moorcroftii and A. nanschanica and at the community level. The relationships between the R-S and M b-M a exhibited different slopes for the alpine plants across all the management practices. Compared to the fenced grasslands, the plants in the grazing blocks not only allocated more biomass to the roots but also to the leaf meristems. The present study highlights the contribution of leaf meristems to the accurate assessment of shoot and belowground biomasses. The R/S and M b/M a should be cautiously used in combination in the future research. The understanding of the distinction between the R-S and M b-M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.

No MeSH data available.


Related in: MedlinePlus

Differences between the R/S and Mb/Ma at both the species and community level for each of four management blocks (A–D). The differences between R/S and Mb/Ma for each same species and the combined community (E–H). The relationships of the belowground‐aboveground biomasses and root‐shoot biomasses at both the species and community levels on the Tibetan alpine grassland (I–L). All regression lines are shown for the relationships that were significant at P < 0.0001. Different letters indicate significant differences between the R/S and Mb/Ma values (P < 0.05).
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ece32059-fig-0002: Differences between the R/S and Mb/Ma at both the species and community level for each of four management blocks (A–D). The differences between R/S and Mb/Ma for each same species and the combined community (E–H). The relationships of the belowground‐aboveground biomasses and root‐shoot biomasses at both the species and community levels on the Tibetan alpine grassland (I–L). All regression lines are shown for the relationships that were significant at P < 0.0001. Different letters indicate significant differences between the R/S and Mb/Ma values (P < 0.05).

Mentions: The Mb/Ma was significantly higher than the R/S at both the species and community levels across the four management blocks (P < 0.05; Fig. 2A–D). When the individuals of the same species (S. purpurea, C. moorcroftii, and A. nanschanica) and the 16 quadrats of community were aggregated, the Mb/Ma was also higher than the R/S (P < 0.05; Fig. 2E–H). The use of Mb/Ma to express R/S appeared to overestimate the actual value of the R/S in the alpine grassland at both the species and community levels. For S. purpurea, the Mb/Ma was three times higher than the R/S. The Mb/Ma was approximately two times higher than the R/S for species of C. moorcroftii and A. nanschanica and at the community level. Many studies have ignored the proportion of the leaf meristem biomass, which belongs to the shoot portion but is located below the soil surface. In the alpine ecosystems, the leaf meristems are buried several centimeters below the soil surface. In addition, the buried depth differed in plant species and phylogeny. The leaf meristems of grasses and sedges (e.g., S. purpurea and C. moorcroftii) are buried 1–3 cm below the ground, while leaf meristems of some cushion plant (e.g., Arenaria pulvinata) are only at a depth of 0.5–1 cm. The diurnal variations in soil temperature are small, and thus, buried meristems are typical evidence of the morphological avoidance of extremely low temperatures (Körner 2003). Furthermore, this allocation mechanism is also conducive to avoiding the zone of severe surface heating during times of intense direct solar radiation, large grazing animals and mechanical damage (Körner 2003). The allocation is a vital survival mechanism for plants to overcome extreme alpine environments.


Leaf meristems: an easily ignored component of the response to human disturbance in alpine grasslands.

Hong J, Ma X, Wang X - Ecol Evol (2016)

Differences between the R/S and Mb/Ma at both the species and community level for each of four management blocks (A–D). The differences between R/S and Mb/Ma for each same species and the combined community (E–H). The relationships of the belowground‐aboveground biomasses and root‐shoot biomasses at both the species and community levels on the Tibetan alpine grassland (I–L). All regression lines are shown for the relationships that were significant at P < 0.0001. Different letters indicate significant differences between the R/S and Mb/Ma values (P < 0.05).
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834318&req=5

ece32059-fig-0002: Differences between the R/S and Mb/Ma at both the species and community level for each of four management blocks (A–D). The differences between R/S and Mb/Ma for each same species and the combined community (E–H). The relationships of the belowground‐aboveground biomasses and root‐shoot biomasses at both the species and community levels on the Tibetan alpine grassland (I–L). All regression lines are shown for the relationships that were significant at P < 0.0001. Different letters indicate significant differences between the R/S and Mb/Ma values (P < 0.05).
Mentions: The Mb/Ma was significantly higher than the R/S at both the species and community levels across the four management blocks (P < 0.05; Fig. 2A–D). When the individuals of the same species (S. purpurea, C. moorcroftii, and A. nanschanica) and the 16 quadrats of community were aggregated, the Mb/Ma was also higher than the R/S (P < 0.05; Fig. 2E–H). The use of Mb/Ma to express R/S appeared to overestimate the actual value of the R/S in the alpine grassland at both the species and community levels. For S. purpurea, the Mb/Ma was three times higher than the R/S. The Mb/Ma was approximately two times higher than the R/S for species of C. moorcroftii and A. nanschanica and at the community level. Many studies have ignored the proportion of the leaf meristem biomass, which belongs to the shoot portion but is located below the soil surface. In the alpine ecosystems, the leaf meristems are buried several centimeters below the soil surface. In addition, the buried depth differed in plant species and phylogeny. The leaf meristems of grasses and sedges (e.g., S. purpurea and C. moorcroftii) are buried 1–3 cm below the ground, while leaf meristems of some cushion plant (e.g., Arenaria pulvinata) are only at a depth of 0.5–1 cm. The diurnal variations in soil temperature are small, and thus, buried meristems are typical evidence of the morphological avoidance of extremely low temperatures (Körner 2003). Furthermore, this allocation mechanism is also conducive to avoiding the zone of severe surface heating during times of intense direct solar radiation, large grazing animals and mechanical damage (Körner 2003). The allocation is a vital survival mechanism for plants to overcome extreme alpine environments.

Bottom Line: The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels.The R/S and M b/M a should be cautiously used in combination in the future research.The understanding of the distinction between the R-S and M b-M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China; University of Chinese Academy of SciencesBeijing100049China.

ABSTRACT
Grazing and fencing are two important factors that influence productivity and biomass allocation in alpine grasslands. The relationship between root (R) and shoot (S) biomass and the root:shoot ratio (R/S) are critical parameters for estimating the terrestrial carbon stocks and biomass allocation mechanism responses to human activities. Previous studies have often used the belowground:aboveground biomass ratio (M b/M a) to replace the R/S in alpine ecosystems. However, these studies may have neglected the leaf meristem biomass, which belongs to the shoot but occurs below the soil surface, leading to a significant overestimation of the R/S ratio. We conducted a comparative study to explore the differences between the R/S and M b/M a at both the species (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) and community levels on a Tibetan alpine grassland with grazing and fencing management blocks. The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels. For S. purpurea, the M b/M a was three times higher than the R/S. The M b/M a was approximately two times higher than the R/S for the species of C. moorcroftii and A. nanschanica and at the community level. The relationships between the R-S and M b-M a exhibited different slopes for the alpine plants across all the management practices. Compared to the fenced grasslands, the plants in the grazing blocks not only allocated more biomass to the roots but also to the leaf meristems. The present study highlights the contribution of leaf meristems to the accurate assessment of shoot and belowground biomasses. The R/S and M b/M a should be cautiously used in combination in the future research. The understanding of the distinction between the R-S and M b-M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.

No MeSH data available.


Related in: MedlinePlus