Protection of the environment by returning farmland to forest and grassland through enclosing areas of land to permit regeneration of native flora is being implemented in the Loess hill region of China. Soil physical properties are important components of ecological systems, as comparisons between cultivated and enclosed areas demonstrate. The results showed: the soil moisture content in the enclosed area was 14.6% and that in the cultivated area was 14%; the soil bulk density and soil porosity were respectively 1.45 g/cm3 and 45.28% in the enclosed areas, and respectively 1.46 g/cm3 and 44.79% in cultivated land. The alteration of soil physical properties was not big between cultivated areas and enclosed areas in the short term.
The three principal fates of axillary meristem in flowering plants are growth (G), reproduction (R), and inactivity (I). The allocation relationships between each meristem and plant size in annual herbaceous plants tend to change with altered precipitation (P) patterns in arid and semiarid grasslands. Here, we examined the allometry and plasticity of meristem allocation in three dominant annual herbaceous plants: Setaria viridis, Corispermum macrocarpum, and Bassia dasyphylla in a semiarid sandy grassland in northern China. We determined the range of plant sizes for each of the three species in the following treatments: ambient environment (Amb), P increased by 30% (P[+]) and by 60% (P[++]), P decreased by 30% (P[−]) and by 60% (P[− −]), drought for 46 days from May 1st to June 15th (D1) and from July 1st to August 15th (D2). We found that meristem allocation to branching intensity increased while allocation to apical dominance decreased with increasing plant size under decreased precipitation and seasonal drought. Decreased precipitation and seasonal drought caused the slope of allometry of meristem allocation in the three species to be significantly different from 1. Plasticity of meristem allocation to G, R, and I in S. viridis tended to be significantly greater in August under P(+) and P(++) while in C. macrocarpum tended to be greater in July under P(−), P(− −), D1, and D2. Our findings are important components of an adaptive strategy in annual herbaceous plants throughout the development stage, which will contribute to predict their developmental dynamics in the semiarid sandy grassland under future climate change.
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