Department of Crop and Soil Sciences, Michigan State University, East Lansing, Michigan 48824-1325, USA.
Ecol Appl. 2011 Jun;21(4):1202-10. doi: 10.1890/10-0525.1.
Despite the importance of fungi in soil functioning they have received comparatively little attention, and our understanding of fungal interactions and communities is lacking. This study aims to combine a physiologically based model of fungal growth with digitized images of internal pore volume of samples of undisturbed soil from contrasting management practices to determine the effect of physical structure on fungal growth dynamics. We quantified pore geometries of the undisturbed-soil samples from two contrasting agricultural practices, conventionally plowed (chisel plow) (CT) and no till (NT), and from native-species vegetation land use on land that was taken out of production in 1989 (NS). Then we modeled invasion of a fungal species within the soil samples and evaluated the role of soil structure on the progress of fungal colonization of the soil pore space. The size of the studied pores was > or =110 microm. The dynamics of fungal invasion was quantified through parameters of a mathematical model fitted to the fungal invasion curves. Results indicated that NT had substantially lower porosity and connectivity than CT and NS soils. For example, the largest connected pore volume occupied 79% and 88% of pore space in CT and NS treatments, respectively, while it only occupied 45% in NT. Likewise, the proportion of pore space available to fungal colonization was much greater in NS and CT than in NT treatment, and the dynamics of the fungal invasion differed among the treatments. The relative rate of fungal invasion at the onset of simulation was higher in NT samples, while the invasion followed a more sigmoidal pattern with relatively slow invasion rates at the initial time steps in NS and CT samples. Simulations allowed us to elucidate the contribution of physical structure to the rates and magnitudes of fungal invasion processes. It appeared that fragmented pore space disadvantaged fungal invasion in soils under long-term no-till, while large connected pores in soils under native vegetation or in tilled agriculture promoted the invasion.
尽管真菌在土壤功能中具有重要作用，但它们相对较少受到关注，我们对真菌相互作用和群落的理解也很欠缺。本研究旨在将真菌生长的生理基础模型与未受干扰土壤样本内部孔隙体积的数字化图像相结合，以确定物理结构对真菌生长动态的影响。我们量化了两种不同农业管理方式（传统耕犁（旋耕机）和免耕）下以及 1989 年休耕的本地物种植被土地利用下未受干扰土壤样本的孔隙几何形状。然后，我们在土壤样本中模拟了一种真菌物种的入侵，并评估了土壤结构对真菌在土壤孔隙空间中定殖进程的作用。研究中所涉及的孔隙大小大于等于 110 微米。通过对拟合真菌入侵曲线的数学模型参数进行量化，确定了真菌入侵的动态。结果表明，免耕土壤的孔隙率和连通性显著低于传统耕犁和本地物种植被土壤。例如，最大连通的孔隙体积分别占传统耕犁和本地物种植被土壤处理中孔隙空间的 79%和 88%，而在免耕土壤中仅占 45%。同样，在免耕土壤中，可用于真菌定殖的孔隙空间比例明显大于传统耕犁和本地物种植被土壤处理，并且不同处理间真菌入侵的动态也有所不同。在模拟开始时，免耕土壤样本中真菌入侵的相对速率较高，而在传统耕犁和本地物种植被土壤样本中，入侵遵循更具双曲线的模式，初始时间步的入侵速率相对较慢。模拟结果使我们能够阐明物理结构对真菌入侵过程的速率和幅度的贡献。似乎在长期免耕土壤中，碎片化的孔隙空间不利于真菌入侵，而在本地物种植被或耕犁农业土壤中较大的连通孔隙则促进了真菌入侵。
