异质养分环境下邻株竞争对3个木荷种源干物质积累及氮磷效率的影响

为了探究不同木荷种源混交林和纯林生产力差异原因,采用盆栽试验,模拟异质和同质性森林土壤环境,并设计木荷单植、双株纯植和与杉木混植3种栽植模式,重点研究了异质养分环境下邻株竞争对3个木荷种源(福建建瓯、江西信丰和浙江龙泉种源)干物质积累及氮磷效率的影响。结果表明:与同质养分环境相比,木荷种源在异质养分环境中具有干物质量大,氮、磷吸收效率高的特点,尤以福建建瓯种源优势最大。邻株竞争对木荷种源的干物质量和氮、磷吸收效率影响显著。在异质养分环境中,与杉木邻株竞争时,木荷福建建瓯种源干物质积累量优于单植和双株纯植模式。这与其根冠比和生理可塑性较强有关,混植时,其根冠比明显降低,将更多的干物质分配至叶片,增强了光合能力;同时氮、磷吸收效率也显著提高,进而积累了较高的干物质量,提高了竞争力。相反,混植时江西信丰和浙江龙泉种源氮和磷吸收效率却不同程度地低于其单植或与之相近,根冠比较高,结果影响了干物质积累。同种邻株竞争虽促进了浙江龙泉和江西信丰种源的氮、磷吸收,但抑制了两元素的利用效率,而福建建瓯种源氮、磷效率受影响较小,且明显高于其他种源,从而形成较高的干物质量。以上研究结果表明,福建建瓯种源较高的生物量分配和生理可塑性是其生产力高和生长竞争优势明显主要原因。

Effect of neighborhood competition on dry matter accumulation, nitrogen and phosphorus efficiency of three provenances of Schima superba in a heterogeneous nutrient environment

Pot experiments were used to simulate the heterogeneity and homogeneity of forest soil environment in order to explore the differences in productivity of mixed and pure forests of Schima superba. In addition, three kinds of planting patterns were established, including the single planting, double pure planting, and mixed planting with Chinese fir, for evaluating the effects of competition from neighboring plants on dry matter accumulation, and nitrogen and phosphorus efficiency of three provenances (Jian''ou of Fujian, Xinfeng of Jiangxi, and Longquan of Zhejiang) of S. superba in heterogeneous nutrient environments. The results showed that all the three provenances had high dry mass, and nitrogen and phosphorus absorption efficiency in heterogeneous nutrient environments, particularly in Jian''ou provenance. The effect of competition with neighboring plants on growth, and nitrogen and phosphorus absorption efficiency in three provenances was significant. In the presence of competition from Chinese fir (i.e., in the mixed plantation treatment), the dry matter content in Jian''ou provenance of Fujian was higher than that in the single planting and double pure planting treatments. Dry matter content was related to its root:shoot ratio and physiological plasticity. In the mixed planting treatment, the root:shoot ratio decreased significantly, and more dry matter was distributed in the leaves, thereby enhancing the photosynthetic capacity. Meanwhile, the enhanced nitrogen and phosphorus absorption efficiency improved dry matter quality to enhance competitiveness. However, the nitrogen and phosphorus absorption efficiency of Xinfeng and Longquan provenances in the mixed planting treatment were either inferior or similar to that in single planting, but with higher root:shoot ratio, which affected dry matter accumulation. Intraspecific competition inhibited the nitrogen and phosphorous utilization efficiency, but enhanced their uptake in Longquan and Xinfeng provenances. However, nitrogen and phosphorous uptake in the Jian''ou provenance was little affected by intraspecific competition. it was significantly higher than that in the other provenances, thereby enhancing the dry matter content. The results suggested that the higher biomass allocation and physiological plasticity in the Jian''ou provenance were the main reasons for its high productivity and competitive advantage.