Coupling Of Forest Stand Structure And Forest Function About Rainfall Distribution Of Typical Forests In Northern Hebei Province

Investigation and experiment in three kinds of forests including planted Chinese pine forest, planted larch forest and natural secondary forest (mixed by larch birch and poplar) were completed at Beigou forest farm in Mulan forestry administration in Weichang county of Hebei province in2010,2011. Coupling relationship between water allocation function, environmental function (about meteorology and plant) and stand structure of the forests was studied. Main research results was listed as follows:1. Stepwise regression analysis and response surface quadratic model was used to get the optimal equation to describe the relationship between throughfall rate or stem-flow rate and stand structure&rainfall class of planted Chinese pine forest and planted larch forest.2."Gathering effect" of throughfall in planted Chinese pine forest was common. Throughfall rate under the crown of some individual tree of Chinese pine sometimes exceeded100%, and was far higher than the throughfall rate of adjacent forest gaps and rainfall outside the forest.3. According to the measurement of self-made simple evapotranspiration measuring devices, mean daytime evapotranspiration rate (0.026mm·h-1) during July to September inside the representative planted Chinese pine forest in study area was smaller than the land with no forests (0.065mm·h-1) at most of observation time. Compared with other measuring points inside the forests, daytime evapotranspiration rate of the evapotranspiration device with covering of forest litters, shrub and grass in NO.10sample plot (at later management periods) was higher. During the same time, mean nighttime evapotranspiration rate (0.026mm·h-1) was smaller than the land with no forests (0.065mm·h-1) at during half of observation time. 4. According to the measurement of self-made simple DBH growth measuring devices, sorting (from the highest to the lowest) mean annual DBH growth rate of diameter class-standard trees of planted Chinese pine forest sample plots was as follows:NO.10sample plot (0.2597cm·a-1; with the smaller stand density of600trees·hm-2)> NO.13sample plot (0.2097cm·a-1; with a relatively smaller stand density of1080trees·hm-2) and NO.15sample plot (0.2097cm·a-1; with a relatively smaller stand density of928trees·hm-2)> NO.3sample plot (0.1413cm·a-1; with a higher stand density of2483trees·hm-2), NO.9sample plot (0.1082cm·a-1; with a higher stand density of1408trees·hm-2) and NO.12sample plot (0.1400cm·a-1; with a higher stand density of1815trees·hm-2). Smaller management density was beneficial to increase DBH growth rate of Chinese pine forest. Annual DBH growth rate of planted Chinese pine forest in study area was0.18cm·a-1at mean level during1year, and reached to0.53cm·a-1at DBH growth-peak season during June to September.5. According to factor analysis and canonical correlation analysis, an significant canonical correlation coefficient that reflected the relation between a canonical variable about stand structure and a canonical variable about water allocation function of the forests resched0.9501(P<0.05) and the canonical structure it corresponded showed a well negative correlation between initial directivity of forest stand management and the forest function about permeability and water content.6. Canopy storage capacity without evaporation-considering, trunk storage capacity and trunk drainage partitioning coefficient of all the sample plots of3kinds of forests was summarized. Computed by method of "Leyton-constraint with top5points", canopy storage capacity of No.9-model sample plot (with the forest density of1925trees·hm-2) and No.10sample plot (with the forest density of600trees·hm-2) were0.49mm and0.21mm respectively. In contrast with them, the canopy storage capacity without evaporation-considering of No.9-model sample plot and No.10sample plot were1.03mm and0.74mm in average respectively.7. According to the arithmetic of revised Gash model, Visual Basic language software6.0was used to compile "System for simulation of revised Gash model". This program supports the import of the variables needed for simulation, showing of simulation results and producing and saving of related pictures. The program can simulate dynamic interception loss, stemflow and throghfall, supports the simulation and analysis under the condition of variational parameters, and actualizes sensitivity analysises of canopy parameters that affect canopy interception under the condition that related parameters have been restricted and marked. The program was used to simulate the interception loss, stemflow and throghfall of No.9-model sample plot and No.10sample plot in2011. Sensitivity analysises of canopy parameters to interception was also completed.