Distribution Pattern And Respiration Of Woody Debris Of Hollow-bearing Tree In Middle Mountain Moist Evergreen Broad-leaved Forest Of Ailao Mountains

Hollow-bearing tree is an essential component of forest ecosystems, which plays a key role in animal biodiversity of forest fauna in forest ecosystem. Many forest animals use cavities of hollow-bearing trees for nesting, resting, habitat and feeding sites. The formation of hollow-bearing tree is the result of a series of abiotic and biotic events after the wounding of trunk and branch tissue. Six representative plots (6 ha.) in Xujiaba of Ailao Mountains national nature reserve were chosen. The abundance, DBH (Diameter at Breast Height) class distribution and species composition of hollow-bearing tree, the abundance and composition of cavity were investigated. The distribution pattern of hollow-bearing tree in middle mountain moist evergreen broad-leaved forest of Ailao Mountains was analyzed. The woody debris of hollow-bearing tree was selected and its respiration rate was measured during the rainy season and the dry season in the middle mountain moist evergreen broad-leaved forest of Ailao Mountains, SW China. Furthermore, the correlations among respiration rate, wood density and moisture were analyzed and temperature sensitivity of the respiration rate was simulated. We regressed linearly respiration with wood density, moisture and air temperature in order to confirm the influencing and limiting factors of respiration of woody debris of hollow-bearing tree. The results were as following:1. The average density of hollow-bearing tree was 92.8±11.9 stems·hm-2 and there existed notable variation for different plots. The density and proportion of hollow-bearing tree differed significantly for living trees and standing dead wood (P<0.05). The density of living and standing dead hollow-bearing tree were 82.2±11.8 stems·hm-2 and 10.7±1.1 stems·hm-2 respectively. The proportion of hollow-bearing tree for standing dead wood (18.0±3.2%) was higher significantly than living trees (7.7±0.5) (P<0.05). The DBH class for the living hollow-bearing tree distributed mostly in the class (20≤DBH<40 cm) (28.4%) and least in the class (80≤DBH<100 cm) (3.2%). With the increasing of DBH, the proportion of the living hollow-bearing tree increased markedly. The DBH class for the standing dead hollow-bearing tree also distributed mostly in the class (20≤DBH<40 cm) (46.9%), which was higher significantly than other classes (P<0.05). The species composition of hollow-bearing tree was very abundant. The hollow-bearing tree belonged to 15 families and 34 tree species, which accounted for 83.3% of all families and 68.0% of tree species. The families of hollow-bearing tree distributed in Fagaceae, Theaceae, Lauraceae and Magnoliaceae that were dominating families. The species of hollow-bearing tree distributed mainly in Castanopsis wattii,Lithocarpus xylocarpus,Lithocarpus hancei,Manglietia insignis,Machilus yunnanensis,Schima noronhae and Hartia sinensis.2. The cavities distributed unevenly with their average density 140.3±19.2 hollows·hm-2. There were the most cavities for the type of Trunk middle and the type of Butt Hollow secondly. The cavities for the type of Trunk middle and the type of Butt Hollow were more significantly than the other four types (P<0.05). There was the most cavities for the entrance size class of 5≤d<15 cm, which was more than the other three classes (P<0.05). With the entrance size increasing, the density of cavities decreased dramatically.3. The density of woody debris of inner layer of trunk and hollow was higher significantly than surface layer of trunk of hollow-bearing tree (P<0.05), but the difference of density between inner layer of trunk and hollow was not significant (P >0.05). The respiration rate of surface layer of trunk during rainy season was significantly higher than that of inner layer of trunk and hollow (P<0.05), but the difference of respiration rate during dry season was not significant for three positions (P>0.05). The wood moisture and respiration rate of the surface layer, the inner layer and the hollow were higher during the rainy season than the dry season, and the difference was significant (P<0.01) for the surface layer and hollow,but not significant (P>0.05) for the inner layer. There was negative correlation between wood density and respiration rate, and the correlations for three different positions during rainy season were significant (P<0.01). There was positive correlation between wood moisture and respiration rate for the three different positions during both rainy season and dry season. The temperature coefficient (Q10) for three positions ranks as: Hollow (2.08) > Surface layer (2.01)> Inner layer (1.73), which shows wood debris of hollow was the most sensitive to temperature. The respiration rate of woody debris of hollow-bearing tree was significantly due to the integrative effect of wood moisture, density and air temperature (P<0.001). The low wood moisture during dry season and the cold climate during whole year were key limiting factors for the decomposition of woody debris of hollow-bearing tree in the middle mountain moist evergreen broad-leaved forest of Ailao Mountains, SW China.