The Intensity of Simulated Grazing Modifies Costs and Benefits of Physiological Integration in a Rhizomatous Clonal Plant

Abstract

Clonal plants in grasslands are special species with physiological integration which can enhance their ability to tolerate herbivory stress especially in heterogeneous environments. However, little is known about how grazing intensity affects the trade-off between the benefits and costs of physiological integration, and the mechanism by which physiological integration improves compensatory growth in response to herbivory stress. We examined the effects of simulated grazing intensity on compensatory growth and physiological integration in a clonal species Leymus chinensis with a greenhouse experiment. This experiment was conducted in a factorial design involving nutrient heterogeneity (high-high, high-low, low-high, low-low), simulated grazing by clipping (0%, 25%, 50% or 75% shoot removal) and rhizome connection (intact versus severed) treatments. Compensatory indexes at 25% and 50% clipping levels were higher than that at 75% clipping level except in low-low nutrient treatments. Physiological integration decreased and increased compensatory indexes when the target-ramets worked as exporter and importer, respectively. Generally, clipping increased both benefits and costs of physiological integration, but its net benefits (benefits minus costs) changed with clipping intensity. Physiological integration optimized compensatory growth at light and moderate clipping intensity, and its net benefits determined the high capacity of compensatory growth. Grassland managements such as grazing or mowing at light and moderate intensity would maximize the profit of physiological integration and improve grassland sustainability.

Parasitism induces negative effects of physiological integration in a clonal plant

“…For example, through differential effects on hosts and nonhosts and by decreasing the density of vegetation, parasitic plants can change plant community structure (Press & Phoenix, 2005), promote plant species diversity (Grewell, 2008; Heer et al ., 2018), and control invasive plant species (Shen et al ., 2007; Yu et al ., 2008; Cirocco et al ., 2017; Tĕšitel et al ., 2017, 2020; Li et al ., 2019). Clonal integration may modify the response of plants to grazing (Liu et al ., 2020) and help explain why increased dominance by tall, wide‐spreading clonal plants accounts for much of the negative effects of elevated N levels on diversity in some grasslands (Gough et al ., 2012; Dickson et al ., 2014), and why clonal growth in plants is associated with invasiveness (Pyšek et al ., 1995; Pyšek, 1997; Liu et al ., 2006; Song et al ., 2013). The results here suggest that clonal integration and parasitism also have interactive effects that may substantially modify their independent effects on diversity.…”

The Amelioration of Grazing through Physiological Integration by a Clonal Dune Plant

“…Being grazed thereby decreases the plant’s photosynthetic area and reproductive structures [ 12 , 13 , 14 ], and ultimately impacts on survival [ 15 ]. Clones spanning a patchy grazing regime can potentially compensate for lost tissue within a clone through the transport of photosynthate from ungrazed to grazed portions of a clone, allowing for the production of new photosynthetic tissue [ 16 ]. By spreading the risk of genet death among ramets within a clone, clonal plants can increase the probability of survival in grazed environments [ 17 , 18 ].…”

Sheep Excrement Increases Mass of Greenhouse Gases Emissions from Soil Growing Two Forage Crop and Multi-Cutting Reduces Intensity

“…There have been some important reports on GHG emission inventories from sources of ruminant agriculture based on emission factor methods [16,17] or remote sensing [18], and more field trials are worth implementing in localized emission factor studies. Moreover, studies on the emissions of the three dominant components of GHGs, global warming potential, and the mechanisms of different forage crops should be conducted under a combination of ingestion, excrement, and trampling of grazing livestock, which could be simulated by multi-cutting and animal excrements to a certain extent [19][20][21]. Therefore, we hypothesize that the interaction between multi-cutting and livestock excrement may significantly alter the global warming potential of different forage crop soils, which may exceed the influence of single factors.…”