Effect Of Gap Size On Plant Diversity And Stoichiometric Characteristics Of Dominant Species In Pinus Massoniana Plantation

Masson pine (Pinus massoniana) is one of the main plantation tree species of returning farmland to forest in upper Yangtze river low hilly land, due to long-term taking the single pure specie forest management pattern, the woodland soil fertility, forest productivity and species diversity declined, ecological function droped. In view of the ecological status of Pinus massoniana plantation in the region, felling the Pinus massoniana to form different sized forest gap, then to study the plant composition, species diversity in Pinus massoniana forests and the changement of plant chemical metrological characteristics after gap disturbance, through this study, we expect to find a reference for nearly natural transformation with Pinus massoniana plantations of inefficient, to improve the stability and productivity of plantations, it is of great significance to improve the ecological service function and sustainable management of plantations. This test started since October 2011, we choose the 39 years mature Pinus massoniana plantation in sichuan, artificial cut 7 kinds of sized gap patches, study the plant species composition and diversity, the characteristics of chemical measurement of dominant plants, the results show that:(1) The plants in Pinus massoniana plantation were dominated by phanerophyte plants, followed by the hemicryptophytes, geophytes, and therophyte plants. The phanerophyte plants in plantaions were higer than that in forest gaps. The larger gaps had a abundant phanerophyte plants, the geophytes and therophyte plants in plantations were less than that in smaller gaps.(2) The species richness, dominance, species diversity indices had significant differences in different gaps. The species richness of middle and small gaps were lower than big gaps, the species richness and the species diversity index under forests were significantly lower than gaps. Different from the richness index, dominance index and diversity index, the evenness index under forests and middle gaps were higher, the evenness index of small gaps were lower.(3) The highest diversity appeared in summer, followed by autumn, the lowest diversity was in the spring. The maximum occurred in 1225-1600 m2 gaps, which could promote the recovery of plant diversity and the renewal of the vegetation.(4) Gap size had a significant impact on C and N content of the dominant plants in Pinus massoniana plantation forests, besides Dicranopteris linearis, the P contents of other advantage plants under different forest gaps had significant differences. The C contents of Phytolacca acinosa, Arthraxon hispidus, Miscanthus sinensis, Dicranopteris linearis, Pteridium aquilinum were the largest in 225 m2 gap. The C contents of Miscanthus sinensis, Dicranopteris linearis and Pteridium aquilinum under forest were higher than the average of all gaps, but the C contents of Phytolacca acinosa and Arthraxon hispidus undergrowth were less than the average. The maximum N contents of Phytolacca acinosa, Arthraxon hispidus, Miscanthus sinensis were in 100 or 225 m2 gap, the N content of Dicranopteris linearis and Pteridium aquilinum were the highest in 900 m2 gap, the minimum N contents of five advantage plants were in 1600 m2 gap. The N contents of Phytolacca acinosa, Dicranopteris linearis and Pteridium aquilinum under forest were slightly higher than the average of all gaps, the N contents of Arthraxon hispidus and Miscanthus sinensis under forest were basically equal to the average of gaps. The P contents of Phytolacca acinosa and Pteridium aquilinum under forest were higher than the average of all gaps, the P contents of Arthraxon hispidus, Miscanthus sinensis and Dicranopteris linearis under forest were less than the average of gaps.(5) The carbon nitrogen ratio, carbon phosphorus ratio had significant differences in different size gaps of dominant plants in Pinus massoniana plantation, except Dicranopteris linearis, gap size had a significant impact on nitrogen phosphorus ratio of other dominant plants. The carbon nitrogen ratio of Miscanthus sinensis and Dicranopteris linearis under forest were higher than the average of gaps, the carbon nitrogen ratio of Phytolacca acinosa and Arthraxon hispidus under forest were less than the average. The carbon phosphorus ratio of Miscanthus sinensis and Dicranopteris linearis under forest were significantly higher than the average of gaps, the carbon phosphorus ratio of Phytolacca acinosa, Arthraxon hispidus and Pteridium aquilinum under forest were lower than the average. The nitrogen phosphorus ratio of Miscanthus sinensis and Dicranopteris linearis under forests were higher than the average of all gaps, the nitrogen phosphorus ratio of Phytolacca acinosa and Pteridium aquilinum under forest were below the average of each forest gap. The nitrogen phosphorus ratio of Dicranopteris linearis ranged between 10.5 to 20.8, the nitrogen phosphorus ratio of Dicranopteris linearis in big gaps were less than 14, restricted by N, the nitrogen phosphorus ratio under forests and 400 m2 gap were above 16, restricted by P; The nitrogen phosphorus ratio of Phytolacca acinosa, Miscanthus sinensis and Arthraxon hispidus were basicly less than 14, explained their growth were restricted by N.