植物过度补偿生长(OCG)是植物群落适应环境干扰的重要机制。然而,目前尚不清楚植物OCG是否可以在退化的高山草甸中发生。这里,我们在高山草甸进行了三个退化水平的割草实验(即,严重退化,SD;中度降解,MD;和光降解,LD)于2018-2020年对青藏高原东南部地区进行植物OCG及其与土壤速效养分的关系调查,植物养分利用效率(即,氮的利用效率,NUE;和磷利用效率,PUE),和降水。结果表明,1)植物群落的OCG一般发生在所有降解水平,植物群落的OCG强度随修剪时间的增加而降低。此外,修剪两年后,SD处理的植物群落的OCG强度显着大于MD和LD处理(p<0.05)。2)在LD和MD中,土壤硝态氮(NO3-)和速效磷(AP)浓度呈下降趋势(p<0.05),而从2018年到2020年,土壤铵态氮(NH4+)浓度没有变化(p>0.05)。在SD治疗中,土壤NO3-浓度呈下降趋势(p<0.05),NH4+浓度有增加的趋势(p<0.05),从2018年到2020年,AP浓度呈反抛物线趋势(p<0.05)。3)从2018年到2020年,植物NUE和PUE在所有降解水平均呈下降趋势。4)植物养分利用效率,受复杂的植物-土壤相互作用的调节,沿着每个降解梯度强烈控制植物群落的OCG。此外,降水不仅直接促进植物群落的OCG,而且通过调节植物群落的结构和植物养分利用效率间接影响OCG。这些结果表明,退化的高山草甸植物群落的OCG不仅可以受益于植物-土壤系统的强大自我调节能力,而且还可以受益于潮湿的气候条件。
Plant overcompensatory growth (OCG) is an important mechanism by which plant communities adapt to environmental disturbance. However, it is not clear whether plant OCG can occur in degraded alpine meadows. Here, we conducted a mowing experiment in an alpine meadow at three degradation levels (i.e., severe degradation, SD; moderate degradation, MD; and light degradation, LD) on the southeastern Qinghai-Tibetan Plateau from 2018 to 2020 to investigate plant OCG and its relationships with soil available nutrients, plant nutrient use efficiency (i.e., nitrogen use efficiency, NUE; and phosphorus use efficiency, PUE), and precipitation. The results showed that 1) the OCG of the plant community generally occurred across all degradation levels, and the OCG strength of the plant community decreased with mowing duration. Moreover, the OCG strength of the plant community in the SD treatment was significantly greater than that in the MD and LD treatments after two years of mowing (p < 0.05). 2) In LD and MD, the soil nitrate nitrogen (NO3-) and available phosphorus (AP) concentrations exhibited a decreasing trend (p < 0.05), while the soil ammonium nitrogen (NH4+) concentration did not change from 2018 to 2020 (p > 0.05). In the SD treatment, the soil NO3- concentration tended to decrease (p < 0.05), the NH4+ concentration tended to increase (p < 0.05), and the AP concentration exhibited an inverse parabolic trend (p < 0.05) from 2018 to 2020. 3) From 2018 to 2020, plant NUE and PUE exhibited decreasing trends at all degradation levels. 4) Plant nutrient use efficiency, which is regulated by complex plant-soil interactions, strongly controlled the OCG of the plant community along each degradation gradient. Moreover, precipitation not only directly promoted the OCG of the plant community but also indirectly affected it by regulating the structure of the plant community and plant nutrient use efficiency. These results suggest that the OCG of the plant community in degraded alpine meadows may benefit not only from the strong self-regulating capacity of the plant-soil system but also from humid climatic conditions.