养分在茎和叶之间的再分配驱动着中国内蒙古草原的退化。
Nutrient reallocation between stem and leaf drives grazed grassland degradation in inner Mongolia, China.
机构信息
Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau & Inner Mongolia Key Laboratory of Grassland Ecology, School of Ecology and Environment, Inner Mongolia University, 010021, Hohhot, China.
State Key Laboratory of Vegetation and Environment Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
出版信息
BMC Plant Biol. 2022 Oct 29;22(1):505. doi: 10.1186/s12870-022-03875-4.
BACKGROUND
Decline in height and aboveground biomass of the plant community are critical indicators of grassland ecosystem degradation. Nutrient reallocation induced by grazing occurs among different organs, which balances the trade-off between growth and defense. However, it is not yet clear how nutrient reallocation strategies affect plant community structure and functions in grazed grasslands. A grazing experiment was conducted in a typical steppe in Inner Mongolia, China. We investigated plant community characteristics and measured plant functional traits of dominant species (Leymus chinensis and Cleistogenes squarrosa) at individual and population levels. Carbon (C), nitrogen (N), phosphorus (P), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) concentrations of stem and leaf in the two species were also determined.
RESULTS
N, P, Cu, Fe, Mn, and Zn concentrations in leaves and stems of L. chinensis and C. squarrosa significantly increased with grazing intensity, and microelements (Cu, Fe, Mn, and Zn) were more sensitive to grazing. The nutrient slopes of macro- and microelements in leaves were significantly higher than those in stems under grazing, indicating that nutrient resources were preferentially allocated to leaves and enhanced the compensatory growth of leaves in the grazed grassland. With increasing grazing intensity, the aboveground biomass of stems and leaves in the two species significantly decreased, but leaf to stem ratio increased at the individual level, indicating that plants preferentially allocated biomass to leaves under grazing. The increase in leaf to stem ratio due to nutrient reallocation between the two organs significantly reduced height and aboveground biomass at population and community levels, driving grassland ecosystem degradation.
CONCLUSION
Our study revealed the driving forces of community structure and function degradation in grazed grasslands from the perspective of nutrient resource allocation, and provided insights into plant adaptation strategies to grazing.
背景
植物群落高度和地上生物量的下降是草地生态系统退化的关键指标。放牧引起的养分再分配发生在不同器官之间，从而平衡了生长和防御之间的权衡。然而，目前尚不清楚养分再分配策略如何影响放牧草地的植物群落结构和功能。本研究在中国内蒙古典型草原进行了放牧实验。我们在个体和种群水平上调查了植物群落特征，并测量了优势物种（羊草和糙隐子草）的植物功能性状。还测定了两种植物茎和叶中的碳（C）、氮（N）、磷（P）、铜（Cu）、铁（Fe）、锰（Mn）和锌（Zn）浓度。
结果
羊草和糙隐子草的叶片和茎中 N、P、Cu、Fe、Mn 和 Zn 浓度随放牧强度的增加而显著增加，微量元素（Cu、Fe、Mn 和 Zn）对放牧更敏感。在放牧下，叶片中宏量和微量元素的养分斜率明显高于茎，表明养分资源优先分配到叶片，并增强了放牧草地中叶片的补偿生长。随着放牧强度的增加，两种植物的地上茎和叶生物量显著减少，但个体水平上的叶茎比增加，表明植物在放牧下优先将生物量分配给叶片。由于两个器官之间的养分再分配，叶茎比的增加显著降低了种群和群落水平的高度和地上生物量，从而导致草地生态系统退化。
结论
本研究从养分资源分配的角度揭示了放牧草地群落结构和功能退化的驱动力，并为植物对放牧的适应策略提供了新的见解。
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