Effects of closed forest on diameter class structure ofQuercus mongolica forest in eastern area of Xiaoxing’an Mountains

Abstract

In eastern area of Xiaoxing’an Mountains, Heilongjiang Province (44 ^o4′–47 ^o26 N′, 126 ^o33′–131 ^o41 E′) the diameter-class structure ofQuercus mongolica forest after different closed time was studied in the plots with different slope direction. Six repetitive plots within 5-year, 16-year and 24-year closedQ. mongolica forests were selected in sunny slope and shade slope, respectively. The area of each plot was 20m×20m. Diameter at breast height (DBH), tree height and canopy diameter of all the trees were measured. Six classes of diameter were determined as 2, 4, 6, 8, 10, and 12 depending on the range of DBH (0–3, 3–5, 5–7, 7–9, 9–11, and 11–13 cm). The results showed that: 1) After 5-year closed treatment, the population quantitiesQ. mongolica, Tilia mandshurica andUlmsis laciniata decreased with the increase in diameter class, which indicated they were healthy populations; 2) After 16-year closed treatment the tree number ofTilia mandshurica andUlmsis laciniata decreased because of canopy coverage increasing and became the associated species inQ. mongolica population; 3)Q. mongolica, after 24-year closed treatment, became dominant species; 4) Canopy coverage increased more rapidly in sunny slope than that in shade slope. Recession ofTilia mandshurica andUlmsis laciniata populations in sunny slope was more obviously than that in shade slope.

Keywords

Closed forest / Q. mongolica forest / Diameter-class structure / S755 / A