Functional trait variability and phenotypic plasticity are the main mechanisms plants use to respond to heterogeneous habitats. These can determine how well a plant grows and where it is distributed. In the Xingdoushan National Nature Reserve, we assessed the response of the functional traits of a population of Metasequoia glyptostroboides parent trees to tree morphology, terrain factors and human disturbance. We found that the leaf area (LA), leaf dry weight (LDW) and specific leaf area (SLA) had large variation and great plasticity, while leaf dry matter content (LDMC) and twig dry matter content (TDMC) were more stable. Human disturbance and the four terrain factors together explained 5%-20% of variance for each functional trait, and crown size explained 38% and 76% of the variation in TDMC and LDMC, respectively. The five functional traits were mainly affected by altitude, slope aspect and human disturbance. The SLA responded slightly to environmental factors and disturbance pattern, while LA and LDW generally increased with strong disturbance. LDMC and TDMC were most sensitive to change in slope aspect. Taken together, the population of M. glyptostroboides parent trees demonstrated significant plasticity in response to the environment through its variability in functional traits. Because human disturbance had a great influence on the growth of these trees, artificial regeneration is recommended, and the impact of agriculture and human construction needs to be reduced.