## 2 Material and Methods  
### Study Site Description  
The study was conducted at Lascessas, TN, USA. The primary soil type was Hillwood gravelly silt loam (12% to 20% slopes, Alfsiol, thermic Oxyaquic Fraglossudalf). The long-term (>30 years) average annual precipitation and mean annual temperature were 1397 mm and 15 \({}^{\circ}\)C, respectively. The entire pasture was measured as 12.8 ha with the geometric center located at the latitude of 35\({}^{\circ}\)53\({}^{\prime}\)19.66\({}^{\prime\prime}\) N and the longitude of 86\({}^{\circ}\)16\({}^{\prime}\)23.77\({}^{\prime\prime}\) W. The grassland pasture was originally established in 2008 and was dedicated for hay production or periodical cattle grazing. It was primarily managed as a cool-season grass dominated natural pastoral ecosystem without application of chemical fertilizers, pesticides, or herbicides. No grazing activities were allowed since the establishment of the EC towers in late 2016. Biomass harvest was performed when the majority of the cool-season grasses reach boot stage. In particular, hay was harvested, cured, and baled from the entire pasture twice in (17 July and 6 September) 2017 and (15 July and 17 September) 2018. Botanical composition was evaluated before EC data collection in late 2016, indicating \(\sim\)40% of tall fescue, \(\sim\)10% of Kentucky bluegrass, \(\sim\)20% of orchardgrass, and \(\sim\)30% of other forbs and legumes. Warm-season grass encroachment (35-40% of botanical composition) was typically observed during the hot summer months to early fall (July to August) mainly consisting of purpletop (_Tridens flavus_ ([PERSON]), johnsongrass (_Sorghum halepense_ ([PERSON]), and dallisgrass (_Paspalatum dilatatum_ [PERSON]); and the warm-season grass population dwindled rapidly in late fall (September to October).  
The entire EC-tower system was established in late August 2016 and was continuously recording data until late August of 2018. This time window included two complete growing cycles of typical cool-season grasses which starts from the beginning of the stockpiling season (or fall-planting season) in the early autumn to the end of summer-dormancy season of the following year. In Middle Tennessee, fall-planting (from late August to Middlepember) of cool-season grasses is generally preferred for controlling weed outbreak and _Sclerotinia homoecarapa_ [PERSON]. [PERSON] infection [12] compared to spring planting. The detailed patterns of daily average ambient air temperature (Tair), soil volumetric water content (SVWC), and precipitation during each growing season are shown in Figure 1.  
In particular, the cumulative growing-season precipitation was 1212 and 1353 mm; and the average Tair was 15.8 and 14.3 \({}^{\circ}\)C for the first and the second growing seasons, respectively. The average SVWC was 26.6 and 31.4% with the values mostly between 8.6 to 36.2% and 18.4 to 39.7% during the two consecutive gro  
Figure 1: Daily ambient air and soil temperature (top), precipitation, and soil volumetric water content (SVWC, bottom) of a grass-dominated grassland ecosystem from the 2016–2017 and 2017–2018 growing seasons located in Middle Tennessee. Dashed lines separate years from each other.