Impacts of nitrogen enrichment on vegetation growth dynamics are regulated by grassland degradation status

文献类型： 外文期刊

第一作者： Xu, Xiaotian

作者： Xu, Xiaotian;Lu, Shaowei;Li, Shaoning;Zhao, Na;Hu, Guozheng;Liu, Xu

作者机构：

关键词： continuous photography; degraded grassland; nitrogen addition; phenology; plant cover

期刊名称：LAND DEGRADATION & DEVELOPMENT （ 影响因子：4.977； 五年影响因子：5.291 ）

ISSN： 1085-3278

年卷期：

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收录情况： SCI

摘要： Plant phenological responses under global climate change is a hot topic in current ecological research. However, it also has comprehensive interactions with other anthropogenic environmental factors including nitrogen (N) enrichment owing to atmospheric deposition and fertilization, and grassland degradation, which attracts less attention. Continuous photographic techniques enabled us to monitor the plant cover dynamics and extract the phenophases (start, end, length and the peak cover position of growing season) in a field experimental platform with six N treatment levels on five grasslands along a degradation gradient indicated by a human disturbance index (HDI). The results showed that N addition significantly promoted seasonal plant covers of degraded grasslands, while mature grassland responding less sensitively. Moreover, increasing rates during spring green-up and decreasing rates during autumn senescence were promoted by N addition, while those of grasslands with lower degradation levels showed non-linear saturation patterns. Phenophases at the community level were generally insensitive to N addition, with the most degraded grassland (totally degraded grassland, TD) and mature grassland (MG) responding significantly. The length of growing season of TD was shortened by 8 days and that of MG lengthened by 15 days on average from N addition. The responses of extracted phenophases were regulated more by the proportions of three groups of degradation indicators (annuals, moderate grazing degradation indicator species, and climax species) than those of grasses and forbs. Our findings highlight the relationship between community phenology and grassland degradation, which can benefit the assessment and restoration of degraded grasslands in semiarid regions.

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