Soil Amendment Effects on Degraded Soils and Consequences for Plant Growth and Soil Microbial Communities

Human activities that disrupt soil properties are fundamentally changing ecosystems. Soil degradation decreases microbial abundance and activity, leading to changes in nutrient availability, soil organic matter, and plant growth and establishment. Land use and land cover change are widespread and increasing in semiarid regions of the southwestern US, which results in reductions of native plant and microbial abundance and community diversity. Here we studied the effects of soil degradation and amendments (biochar and woodchips) on microbial activity, soil carbon and nitrogen availability, and plant growth of ten semi-arid plants species native to the southwestern US. Results show that woodchip amendments result in poor overall plant growth, while biochar amended soils promoted plant growth when soil quality was reduced. Additionally, amendments had a strong influence on microbial activity, while the presence and species identity of plants did not. Biochar amended soils led to increases in the potential activities of enzymes involved in the degradation of carbon, nitrogen, and phosphorus rich substrates. Woodchips, caused an increase of potential activity in enzymes involved in the degradation of sugar and proteins. These results show that microbes and plants respond differently to soil treatments and suggest that microbial responses may function as earlier indicators of the success of re-vegetation attempts.