## 4 Discussion  
### Different Drought Resistance of the Plant Species  
In this study, drought significantly increased the coverage of _Heteropappus altaicus_, _Potentilla bifurca_, and _Artemisia scoparia_, but did not affect the coverage and abundance of _Agropyron cristatum_, _Stipa kijlovii_, and _Cleistogenes squarrosa_. The various types of coverage and abundance responses to drought stress indicate that the resistances of the plant species are species-specific. Reductions in coverage and abundance induced by drought for some species are not surprising. Most of the previous studies have shown that plant cover and density decreased under a low water availability environment [36; 37; 38], especially in the arid and semi-arid areas [39]. This result is easy to understand. Water is an important resource for plant growth and the primary limitation of plant growth in the semi-arid grassland [11; 35]. Plants wilt or even die when the external environment lacks water. Too many previous studies have reported that drought-induced changes in community cover and abundance are closely associated with the variation of soil moisture [16]. The neutral response of cover and abundance is also easily explained. Some drought tolerance species  
Figure 4: Pearson correlation coefficients (r) between soil microbial PLFAs and soil physicochemical properties at 0–10 cm soil LBR (leaf biomass ratio), RL (root length/root depth), RC (root shoot ratio), RBR (root biomass ratio), RRCD (response ratio of coverage to drought), RRAD (response ratio of abundance to drought), RRCR (response ratio of coverage during the recovery stage), RRAR (response ratio of abundance during the recovery stage). *, significant correlations between the two variables at the level \(p<0.05\). Figure 5: Relationships of changes of cover with leaf biomass ratio (**a**); changes of abundance with leaf biomass ratio (**b**) under the drought; and changes of abundance with root biomass ratio (**c**). Abbreviations as Figure 4.  
are not sensitive to short time drought stress [8, 40]. Our drought treatment was only conducted for two months, and the last survey was only 56 days from the beginning of drought treatment. Unchanged coverage and abundance for the nine species indicated that the nine target species had a certain size of individuals and drought resistance at the beginning of the experiment. Some species can resist this short-term drought, although this period of precipitation accounts for a large proportion of the annual precipitation [15]. The results indicated that a long-term study must be conducted to confirm the effect of drought on plant performance; however, increased abundance and coverage of some species under drought treatment in our study have been rarely reported in previous studies. Only a few experiments have reported increasing dominance of drought-tolerant species with available water reduction [35]. The elevating coverage and abundance of the three species under drought can be ascribed to two possible reasons. First, these three species (_Heteropappus altaicus_, _Potentilla bifurica_, and _Artemisia scoparia_) have a relatively large leaf biomass ratio. The leaf biomass ratio explained 57% and 45% variations of the cover and abundance under drought, which have demonstrated that species with larger leaf biomass ratios are more tolerant to drought (Figures 4 and 5). In addition, these three species have relative deep root depth [41], which can help to explain their greater drought resistance potential. Moreover, the responses of different species to drought stress are also related to their own morphological characteristics. In this study, the legume plant species _Artemisia scoparia_ is relatively high among the nine species [41], which could inhibit the growth of lower plants through the shading effect [42]. These results show that the interaction between plant functional groups regulates the response of the plant community to the change of precipitation [36, 42], which can also explain the different responses of dominated species to drought.