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| 1 | Effects of grassland management on the community structure, aboveground biomass and stability of a temperate steppe in Inner Mongolia, China显示文摘Plant community structure responds strongly to anthropogenic disturbances, which greatly influence community stability. The changes in community structure, aboveground biomass(AGB), biodiversity and community stability associated with different management practices were studied with a three-year field investigation in a temperate steppe of Inner Mongolia, China. The species richness, Shannon-Wiener index, evenness, plant functional type abundance, AGB, temporal community stability, summed covariance, scaling coefficient and dominant species stability were compared among areas subjected to long-term reservation(R), long-term grazing(G), mowing since enclosure in 2008(M) and grazing enclosure since 2008(E). Site R had higher perennial grass abundance and lower species richness than sites G, M and E, although the AGB was not significantly different among the four sites. The species structure varied from a single dominant species at site R to multiple dominant species at sites G, M and E. The long-term reservation grassland had lower biodiversity but higher stability, whereas the enclosed grassland with/without mowing had higher biodiversity but lower stability. Different stability mechanisms, such as the compensatory dynamics, mean-variance scaling and dominant species stability were examined. Results showed that community stability was most closely related to the relative stability of the dominant species, which supports the biomass ratio hypothesis proposed by Grime. | ZHANG Jinghui HUANG Yongmei CHEN Huiying GONG Jirui QI Yu YANG Fei LI Engui | 2016 | Journal of Arid Land2016，8，3： | 6 |
| 2 | Effects of vegetation types on soil water dynamics during vegetation restoration in the Mu Us Sandy Land, northwestern China显示文摘The arid and semi-arid northwestern China has been undergoing ecological degradation and the efforts to reverse the ecological degradation have been undertaken for many years. Some shifting dunes have been fixed and the vegetation has been partially recovered in certain areas and the Mu Us Sandy Land in the Ordos Plateau is an example of the success. The present study attempts to reveal the relationships between the vegetation restoration and ecohydrology in the Mu Us Sandy Land. We continuously measured soil water content at 10-min intervals under three vegetation types(i.e., shifting dune, shrub-dominated community, and herb-dominated community) in the Mu Us Sandy Land from April 2012 to October 2013. The results show the infiltration coefficient increased with increased rainfall amount and eventually reached a stable value. Infiltration coefficients were 0.91, 0.64, and 0.74 in the shifting dune, in the shrub-dominated community, and in the herb-dominated community, respectively. Cumulative infiltration and soil texture are two vital factors affecting the depths of rainfall penetration. Only rainfall events larger than 35.0 mm could recharge soil water at the 60–80 cm layer in the herb-dominated community. Our results imply that the expected forward succession of restored vegetation may be destined to deterioration after reaching the climax simply because of following two facts:(1) soil water is mainly retained at shallower layer and(2) plant fine roots mainly distribute in deeper layer in the herb-dominated community. | Yu Xiaona Huang Yongmei Li Engui Li Xiaoyan Guo Weihua | 2017 | Journal of Arid Land2017，9，2： | 6 |
| 3 | Responses of plant^(15)N natural abundance and isotopic fractionation to N addition reflect the N status of a temperate steppe in China显示文摘Aims Elevated anthropogenic nitrogen(N)deposition could alter N status in temperate steppe.However,threshold observations of N status change from N limit to N saturation by far are not conclusive in these ecosystems.Research on the natural abundance of ^(15)N( δ^(15)N)could greatly help provide integrated information about ecosystem N status.The goal of this study was to investigate the suitability of measurements of δ^(15)N of major ecosystem N pools and several key species,plant ^(15)N fractionation,together with key vegetation and soil indicators in response to N fertilization as a tool to identify the N status in a temperate steppe in Inner Mongolia.Methods We carried out a N addition experiment during 2011-14 on a Stipa krylovii steppe in Inner Mongolia,Northern China.We investigated the response of several key N transformation processes,vegetation and soil properties to N addition.Aboveground biomass and below-ground biomass(BGB) δ^(15)N,root and foliar δ^(15)N of three dominant species(Artemisia frigida,S.krylovii and Leymus chinensis), δ^(15)N of soil total N and soil KCl-extractable NO_(3)^(−)-N were determined.The responses of isotope fractionation during plant N uptake and reallo-cation to N addition were also determined.Important Findings Our results suggest that the N addition rate of 5g N m^(−2) yr^(−1) could be regarded as threshold of early N saturation in this S.krylovii steppe as indicated by an increase in plant fraction-ation and a decrease in plant δ^(15)N.When N input rate is>10 g N m^(-2) yr^(-1),increased N deposition can lead to an apparent reduction in species richness and BGB as well as an increase in NO_(3)^(−)in extractable soil pools<30-cm soil profile.With N addition,S.krylovii and A.frigida undergo earlier N status shift from N limitation toward N excess compared with L.chinen-sis,contributing to L.chinensis out-competing other species.Overall,this study provides a better understanding of N status change in temperate steppe based on isotope evidence and several other functional variables and contributes to predicting the responses of temperate steppe to future global N deposition scenario. | Zhilu Sheng Yongmei Huang Kejian He Narigele Borjigin Hanyue Yang Huiying Chen Engui Li Xia Xu Lei Duan | 2019 | Journal of Plant Ecology2019，12，3： | 0 |
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