Effects of cultivation practices on fruit yield, growth and leaf physiology of energy tree species Sapindus mukorossi in China: a meta-analysis

The energy-economy crop Sapindus mukorossi Gaertn. (S. mukorossi) has the potential to cope with energy transition while providing benefits such as saponin by Nature-based Solutions (NbS). However, its industrial development has long been limited by bottlenecks such as unstable raw material supply and compositional fluctuations. In this meta-analysis, we collected 2124 observation pairs from 43 publications in China to explore the effects of cultivation measures on S. mukorossi fruit yield, tree growth and leaf physiological characteristics. The results indicated that cultivation measures including fertilization, trimming, soil acidification, seed treatment and coercion had significant effects in promoting yield (51.0%), tree growth (14.89–31.0%) and leaf physiology (-29.9–19.0%) of S. mukorossi. Among measures, fertilization significantly contributing to fruit yield (95.0%) and aboveground biomass (81.0%) improvement by directly boosting nutrient supply and optimizing leaf phosphorus (19.0%) and potassium (14.9%) partitioning, while trimming enhanced photosynthetic capacity through light energy redistribution and growing canopy (67.7%), creating growth synergism with fertilization. In addition, elevation, climate, and soil properties modulated the effectiveness of cultivation measures through “energy-matter” coupling, with total nitrogen and temperature constituting the strongest promoter and suppressor, respectively, while soil total potassium dominated the response intensity through multiple modulation of increase and decrease effects. This study provides useful insights for the development of site-adapted management and efficient cultivation technology system of S. mukorossi plantation, which could support a nature-friendly model to empower the regional energy transition and the upgrading of the circular economy chain.