Native Perennial Vegetation Buffer Strips Improve Structural Indicators of Riparian Protection in Mediterranean Agroecosystems

ABSTRACT

Riparian zones in Mediterranean agroecosystems are highly vulnerable to degradation because cultivation often reaches stream edges and annual vegetation senesces during the late‐summer dry period, leaving soils exposed when the first erosive autumn rains occur. Vegetation buffer strips (VBS) are widely promoted to reduce erosion and nutrient losses, yet multi‐year field evidence for intentionally established native perennial herbaceous VBS under Eastern Mediterranean seasonality remains scarce. We established a large‐scale riparian experiment along the Nahalal stream in northern Israel, comparing native perennial herbaceous VBS with conventional wheat cultivation and unmanaged spontaneous annual vegetation. VBS were established through mechanical clearing, surface scraping, soil solarization, sowing, and short‐term irrigation. Across five seasonal campaigns over three years, we measured vegetation cover, bare soil, above‐ and belowground biomass, plant richness, surface‐soil organic matter, total nitrogen, nitrate, and Olsen‐P. VBS rapidly established and maintained higher cover, lower bare‐soil exposure, greater above‐ and belowground biomass, and higher observed plant richness than both annual treatments. Contrasts were strongest during the autumn dry‐to‐wet transition, when wheat plots were bare and spontaneous vegetation had largely senesced. VBS also had greater shallow root biomass; a one‐time excavation confirmed rooting to 60–70 cm, although these measurements were not directly comparable with repeated shallow sampling. Soil responses were less consistent. Nitrate and Olsen‐P differed among treatments during parts of the study, but likely reflected establishment practices, site heterogeneity, and perennial vegetation processes rather than direct evidence of reduced nutrient export. Soil organic matter and total nitrogen changed little during the first three years. This study provides one of the first multi‐year field evaluations of intentionally established native perennial herbaceous VBS in an Eastern Mediterranean agroecosystem and identifies the autumn transition as a critical management window. Native perennial VBS can reduce seasonal bare‐soil exposure and strengthen structural riparian protection, although direct long‐term measurements of runoff, sediment, and nutrient export are needed to confirm functional recovery.