Joint forcing by heat waves and mowing poses a threat to grassland ecosystems: Evidence from a manipulative experiment

Abstract

The frequency and intensity of heat waves (HWs) have increased in recent years, but it remains unclear how grassland ecosystems respond to such extreme weather. A 3‐year manipulative field experiment was conducted to simulate HWs under different mowing intensities in a Stipa krylovii steppe on the Mongolian Plateau to examine their effects on plant morphology, phenology, and community. At the species level, the morphology and phenology of the three main herb species (S. krylovii, Melilotoides ruthenica, and Potentilla tanacetifolia) showed species‐specific responses to the HW and mowing treatments. The major dominant species S. krylovii shed ~50% of the tiller outer layer to protect the internal tiller from HW stress thereby directly decreasing the heat load and water loss from green plant tissue and indirectly increasing the litter biomass. HWs also caused increases of community index (richness, diversity, and evenness) but also associated with a 30% decrease in the importance value of S. krylovii, whereas mowing enhanced this value by 27%. When HWs were combined with mowing, the joint forcing of mechanical damage and low carbon accumulation aggravated negative effects of stress on plant health and growth, which further decreased community index. We constructed a framework to fully describe the effects of HWs and mowing and their interrelationship on different ecological levels and explain how short‐term effects, such as extreme climate, produce long‐term effects on ecosystems. In conclusion, we found that synergisms between climate extremes (HWs) and human activities (mowing) can reduce ecosystem stability posing a threat to the grasslands.

Long‐term drought aggravates instability of alpine grassland productivity to extreme climatic event

“…At our study site, clipping effects on plant community biomass might have been counteracted by the compensatory growth effect (White et al, 2014), which is associated with higher species richness and asynchrony, especially in areas with ample rainfall. In addition, the clipping intensity on our site was relatively light (10 cm above the soil surface), which differed from the previous experiments with heavy clipping intensity at the semiarid grassland sites (Fynn et al, 2004; Qu et al, 2020), so clipping could have negligible effects on species richness, species asynchrony, and dominant species.…”

Sustainability challenges for the social-environmental systems across the Asian Drylands Belt

“…Extreme climatic events have been reported across this region (e.g. heatwaves, droughts, cold winters, sandstorms, flooding) (Mildrexler et al 2006, Groisman et al 2018, Chen et al 2020, Qu et al 2020. On average, the ADB region receives annual precipitation of 306 mm and loses 248 mm via evapotranspiration (ET), resulting in approximately 58 mm water to recharge its soils, streams, and groundwater (table S3).…”

“…Water is the foremost limiting resource for most of the ADB region. Both quantity and quality are increasingly affected by the warming climate, uneven distribution of precipitation, and increased intensity and frequency of extreme physical events, such as dust storms, heatwaves, dzuds, desertification, and drought (Kurnaz 2014, Rao et al 2015, John et al 2018, Qu et al 2020. Turkey-a country with relatively high precipitation (table S3)-is experiencing effects, a threat to its agricultural industry, with increased frequency, and dzuds (extreme cold winters) have increased in frequency and severity, impacting livestock across the Mongolian Plateau and pushing populations into urban areas to find alternative livelihoods (Qi et al 2017, Vova et al 2020.…”

“…Despite being mostly landlocked, this region contains several important migration and trade routes, including the Silk Road, which connects east Asia to the west (Chen et al 2015a, Gutman et al 2020). These connections mean the ADB has played a key role in human civilization and societal development (Banuazizi and Weiner 1994, Diamond 1997, Hansen 2012, Chen et al 2020. The ADB is also an ecologically, socioeconomically, and institutionally diverse region.…”

Diverging Responses of Two Subtropical Tree Species (Schima superba and Cunninghamia lanceolata) to Heat Waves

“…A HW is commonly defined as a period with excessively hot days, usually combined with dry atmospheric and surface soil conditions [3][4][5]. Such extreme thermal climatic events can exert stronger selective pressures on organisms than gradual changes in temperature [6][7][8][9] and could negatively impact the function and survival of plants [10][11][12][13]. Moreover, the increase in HW frequency and intensity are particularly obvious in subtropical regions [10,14].…”