Abstract:【Objective】 Cynodon dactylon is a commonly used herbaceous plant for ecological greening, soil consolidation and slope protection, vegetation restoration, and soil and water conservation. Its developed root system network and unique growth characteristics have a significant impact on the formation and spatial reorganization of soil pores. Current research has mostly focused on the role of the plant’s roots in soil aggregate formation and stability, however, the dynamic impact of root growth on soil pores remains unclear. 【Method】 This study employed a pot experiment, selecting Cynodon dactylon as the model plant and typical purple soil and yellow soil from the mountainous and hilly regions of southwestern China as the culture substrates. Four different treatments were established: purple soil with Cynodon dactylon (G), purple soil control (CK), yellow soil with Cynodon dactylon (YG), and yellow soil control (YCK). The soil profile images under different treatments were continuously collected using the minirhizotron technique. The root traits of Cynodon dactylon and soil pore structure parameters at different stages were quantified through optimized root extraction algorithms and image processing techniques. Combined with statistical analysis, the study explored the dynamic growth of Cynodon dactylon roots and their impacts on the evolution of soil pore structure. 【Result】 The results showed that: (1) Cynodon dactylon grew well in both purple and yellow soils, and the root growth rate was higher in purple soil than in yellow soil. The root length, root surface area, and root volume of Cynodon dactylon in purple soil were nearly three times higher than those under yellow soil cultivation conditions; (2) Compared with the unplanted CK and YCK, the growth of Cynodon dactylon significantly reduced the number of pores, porosity, and fractal dimension of purple and yellow soils, and the reduction effect of roots on soil pores continuously increased with root growth; (3) Redundancy analysis indicated that roots explained 40.60% of the variation in soil pore structure, and root length, root surface area, and root volume were the key root traits that reduced soil pore structure parameters. 【Conclusion】 In summary, through the optimized minirhizotron technique, continuous observation of plant roots and soil pores was achieved on site. It was found that Cynodon dactylon significantly reduced pore number and other parameters during its growth period, providing methodological support for in-situ, non-destructive, and dynamic studies on root-pore interactions, as well as theoretical support for vegetation restoration and soil and water conservation in ecologically fragile areas.

Abstract:[Objective] Generally, root is the main organ of a plant to absorb water and nutrients in soil, and how it grows and distributes is an important indicator of a crop in growth and development. The commonly used methods for monitoring crop root growth, such as the soil drilling and excavation methods, are what we call destructive sampling methods. Although they are usually quite high in accuracy, they are not suitable for in situ monitoring of root growth. Therefore, the minirhizotron technique is recommended as an effective method for in-situ monitoring of crop root growth thanks to its rapid and non-destructive approach.[Method] In order to reveal impacts of salt stress on root growth of wheat, a pot culture experiment was conducted, with soil salt content varying along a gradient from 0.61(CK), 1.61(S1), 2.61(S2), 3.61(S3), 4.61 (S4) to 5.61 g·kg-1 (S5). And the minirhizotron technique was used to- collect digital images of the roots at tillering, reviving, jointing and booting growing stages. Then root length, root length density and their distribution in the soil as affected by salt stress were determined with the aid of the digital image processing technology.[Result] Results show that with the aid of the minirhizotron technique, growth and development progresses of the wheat root in the experiment could be intuitively monitored. In the experiment the root length density obtained with the technique was found to be significantly and positively related with that with the soil drilling method (r=0.91), especially at the jointing and booting stages of the crop. Moreover, comparisons of the root images with the root parameters analysis relative to growing stage of the crop revealed that wheat root distributed mostly in the 0-10 cm soil layer and decreased with soil depth, and that root length decreased with rising soil salt content at all growing stages. For example, at the tillering stage, the root length in treatment S5 (S5, 6.61 g·kg-1) was less than half of that in CK, and at the booting stage it was only one-third of that in CK, indicating that the wheat root growth was greatly inhibited by salt stress. The worst occurred at the booting stage, especially in the treatments with soil salt content higher than 3 g·kg-1. It was mainly because high soil salt content caused the root rust and dead, and the higher the soil salt content was, the more obvious this phenomenon was.[Conclusion] Thus, the minirhizotron technique combined with the image processing technique could be used as a more effective method for obtaining root growth parameters as compared with traditional destructive sampling methods. This paper provides a theoretical basis and technical support for in situ monitoring intuitively of crop root growth in saline soils.