Mixed of arbor-shrub significantly enhanced the drought stress adaptive capacity of plantation forests—An interpretation based on dendroecology

Abstract

Multispecies arbor-shrub mixed stands have long been applied in vegetation restoration of the Chinese Loess Plateau, and are expected to provide better production and ecosystem services than pure stands. However, whether higher species and structural diversity will help mitigate the limitations of drought on plantations growth remain poorly quantified. We collected samples of the arbor Platycladus orientalis Linn. and shrub Caragana korshinskii Kom. under different stand structures with the same site conditions, using dendroecological methods analyzed the resistance, recovery, and resilience of mixed and pure stands in response to extreme drought, and compared the differences of recovery capacity under different tree species and stand structures based on the theory of full resilience. Results suggest that drought has a lag effect on plantations growth. Radial growth of mixed and pure stands was mainly limited by drought stress in autumn and winter of the previous year and late spring and early summer of the current year. The recovery after the extreme drought of both planted P. orientalis and C. korshinskii mixed stands were significantly (p < 0.05) higher than pure stands, and there are tradeoffs between resistance and recovery. Comparing the different tree species, even if the drought-induced P. orientalis growth reduction reaches 58.5% (mixed stands) and 41.6% (pure stands), it still has the possibility of recover fully, while C. korshinskii is difficult to recover to the previous level, and the mixed mode also affects the response of plantations to drought stress. Therefore, the growth habits and adaptability of different planted species to drought stress should be considered in the future afforestation projects, and select tree species with complementary traits for mixed planting. Taken together, these findings have important significance for mitigating the limitations of drought on plantations growth and maintaining the ecological function stability of plantations in the western Loess Plateau.