Structure Configuration And Adjustment Of Water Conservation Forest In The Upper Reaches Of Chishui River

Eco-environmental problems in the upper reaches of Chishui River such as degradation of forest vegetation; reducing of biological diversity; increasing of soil and water loss; and of the filling quantity have impact brewing environment of Maotai liquar and on the ecological system of downstream river. Numerous previous researches on water source conservation forest mainly focused on community scale. In this study, 32 tree species of water conservation forests and 10 forest types were chosen to diagnose their structures and characteristics, and a technology for water conservation forest structure configuration and adjustment was proposed. Plant function groups were used as the dimension conversion tool. In addition, the study of natural quality and water-holding capability of the forest community, species adapted to the community, and the water-holding functional groups were also used as the bases of the research. The following results have been achieved: 1 Plant community characteristicsAccording to the vegetation and soil types differences in the upper reaches of Chishui River, 74 plots were selected and divided into 17 associations using Two-way indicator species analysis, and further divided into grass community stage, bushwood community stage, shrub community stage, high-forest community stage and sub-climax community stage. Along with the consequent progress of succession, the community height increases gradually, the structure tends to be more complex, the species abundance increases, and the diversity of shrub layer is higher than tree layer and herb layer at every stage with the succession of grass community stage, bushwood community stage, shrub community stage, high-forest community stage and sub-climax community stage. In vertical structure, the shrub layer has the highest diversity of species, but the plant diversity index is not high as a whole. High-forest community has the most complex species composition. It is suitable to the growth of shrub and herbs, and it provide the basis for the structure adjustment of forest community. V 2 Adaptability characteristics of 32 tree species(1) The water content was 54.44 %- 80.46 %. The bound water / free water was 0.02- 10.07. The transpiration rate was 0.05- 1.30 g.cm-2.h-1. The water potential was-2.43--14.74 MPa. The relative water deficit was 34.74 %- 69.03 %. The specific leaf area was 230.15- 585.39 cm2.g-1. And the dry matter content was 8.39- 31.83. Of these factors, both specific leaf area and dry matter content were significantly correlated in power function curve with water content, while dry matter content was significantly polynomial relationship to the specific leaf area and relative water deficit.(2) The forest gaps in these stands were mainly small and medium in size, and the light intensity followed the order of gaps > forest edge > forest. The light intensity in gaps was not distinctively correlated with forest gap size and average DBH(diameter at breast height) of edge wood, while following an exponential function with average height of edge wood, where the light intensity decreased with increasing average height. Net photosynthetic rate, transpiration rate, water use efficiency were main factors influencing photosynthetic characteristics. The species were classified into five photosynthetic types as follows: higher photosynthetic rate(Pn)- low transpiration rate(Tr)- high water use efficiency(WUE), low Pn- low Tr- high WUE, low Pn-high Tr- low WUE, low Pn- low Tr- low WUE, and high Pn- high Tr- low WUE. The seedlings of dominant plants in gaps occurred with the highest frequency. Comprehensive analysis showed the forest might be better regenerated when the gap size was 80- 160 m2, and the worse was lower 80 m2.(3) The measurement results of δ13 C in leaf foliage ranged from-26.97‰ to-31.72‰, with an average of(-29.44±1.19) ‰, lower than the general level in China. Studies of tree species and shrubs species showed similar Water Use Efficiency(WUE) and alike foliar δ13C values, as(-29.43±1.16) ‰ and(-29.46±1.29) ‰ respectively. Meanwhile, evergreen and deciduous species had foliar δ13C values of(-29.03±1.07) ‰ and(-29.76±1.21) ‰ respectively, and evergreen species had a relative lower WUE. Species originated from normal landform and karst landform had foliar δ13C values of(-29.29±1.21) ‰ and(-29.49±1.22) ‰ respectively, and similar WUE. Limestone soil, yellow soil, rocky soil and purple soil had foliar δ13C values of(-29.59±1.19) ‰,(-29.29±1.21) ‰,(-29.35±1.23) ‰ and(-29.55±1.53) ‰ respectively, and WUE in the descending order as: yellow soil > rocky soil > limestone soil > purple soil. Our research discovered that foliar δ13C had a significant exponential function relationship with maximum water holding rate and ratio, but not with leaf water contents(P<0.05).(4) Tree species adapting to water environment capacity is ranked as: Vernicia fordii, Bambusa pervariabilis, Broussonetia papyifera, Prunus nalicina, Citrus reticulate, Quercus aliena, Cupressus funebris, Eriobotrya bengalensis, Viburnum chinshanense, Liquidamba formosana, Pinus massoniana, Rhus chinensis, Myricaceae rubra, Pistacia chinensis, Camellia sinensis, Platanus acerifolia, Pyracantha fortuneana, Vitex negundo, Sapium sebiferum, Neosinocalamus affinis, Mallotus barbatus, Cunninghamia lanceolata, Castanopsis fargesii, Nandina domestica, Lindera glauca, Coriaria nepalensis, Populus trinervis, Camellia oleifera, Choerospondias axillaria, Melia azedarach, Toona sinensis, Loropetalum chinense.3 Water holding capacity of 32 tree species(1) The soil maximum water holding capacity of 32 tree species from 0 to 60 cm was about 212- 357.94 mm. The available water content ranges form 11.07 mm to 85.15 mm. Water holding rate is greater than the rate of water loss, and the relationship between the two and the time accorded with power function model.(2) The litters amount was 0.15- 4.50 t.hm-2. The natural moisture content was 10.23 %-137.66%. The maximum water holding depth was 0.04- 1.70 mm. The effective water interception depth was 0.02- 1.27 mm. The maximum water loss depth was 0.01- 0.43 mm. Water holding speed and water loss speed in the earlier stage were greater than that in the later stage, and declined rapidly in the initial stage and tended to be stable in the later stage.(3) The maximum water holding ratio ranged from 0.33 to 1.59. The water holding capacity of leaf surface coat was relatively strong. The water holding ratio was higher than the water loss ratio, and the relationship between water holding ratio, water loss ratio and the time was accorded with power function model.(4) The water storage capacity was significantly correlated with DBH, height and crown length of 32 tree species with a power function, and the relationship can be used for estimation and prediction of canopy hydrological and ecological functions. From the canopy layer, Mallotus barbatus, Quercus aliena and Cupressus funebris had a higher canopy interception rate, and Coriaria nepalensis, Vernicia fordii, Melia azedarach and Toona sinensis had a lower canopy interception rate.(5) The water holding capacity is ranked as: Cunninghamia lanceolata > Nandina domestica > Mallotus barbatus > Platanus acerifolia > Populus trinervis >Neosinocalamus affinis > Vitex negundo > Myricaceae rubra >Bambusa pervariabilis >Toona sinensis > Loropetalum chinense > Liquidamba formosana > Camellia sinensis >Castanopsis fargesii > Pinus massoniana > Eriobotrya bengalensis > Camellia oleifera> Quercus aliena > Lindera glauca > Viburnum chinshanense > Melia azedarach >Rhus chinensis > Citrus reticulate > Cupressus funebris > Choerospondias axillaria >Pyracantha fortuneana >Pistacia chinensis > Broussonetia papyifera > Sapium sebiferum> Prunus nalicina > Coriaria nepalensis > Vernicia fordii. 32 tree species in this area canbe divided into seven water holding functional groups as the low interception- low effectiveretain- low root zone pore- low water conservation Ⅰ, middle interception- low effective retain-low root zone pore- low water conservation Ⅱ, middle interception- low effective retain- lowroot zone pore- middle water conservation III, high interception-high effective retain- high rootzone pore- middle water conservation IV, high interception- middle effective retain- high rootzone pore- high water conservation V, middle interception- middle effective retain- middle rootzone pore- middle water conservation VI and middle interception- high effective retain- middleroot zone pore- middle water conservation Ⅶ. 4 Structure and ability of water conservation function of forest types and adjustmentTen forest plant communities could be defined as four types mudium-high water holding-coniferous forest( ASS. Cupressus funebris, ASS. Pinus massoniana + Cupressus funebris, ASS. Cunninghamia lanceolata + Pinus massoniana), mudium water holding- coniferous forest(ASS. Cunninghamia lanceolata, ASS. Pinus massoniana- Quercus fabri), high water holding-broad-leaved forest(ASS. Bambusa pervariabilis, ASS. Pyracantha fortuneana + Viburnum chinshanense) and low water holding – bamboo and bush forest(ASS. Castanopsis fargesii, ASS. Quercus fabri, ASS. Pinus massoniana).Broad-leaved mixed forest is a general direction for water conservation forest in the upper reaches of Chishui River. Based on previous research, water conservation structure adjustment direction should be based on the structure and function of a high level of succession as the goal of different vegetation. Low water holding – bamboo and bush forest formed water conservation functional group II, VII, the species should be increased functional group III, IV, V, VI, in the high water holding- broad-leaved forest and coniferous forest development. Coniferous forest composed water conservation functional group III, VI, in the high water holding- broad-leaved forest development. High water holding- broad-leaved forest formed water conservation functional group IV, VI, should be maintain the existing forest. Comprehensive analysis showed the forest might be better regenerated when the gap size was range from 80 to 160 m2, because the number and area ratio, Comprehensive environmental index, nutrient levels and are higher, seedlings density is highest.