The Study On Water-holding Capacity Of Fresh Leaf Litter In Limestone And Sandstone Regions Of Chongqing

Water conservation and nutrition return are the most important ecological functions of the forest litter (layers). The water holding capacity of the litter (layer) is determined by the litter storages and litter hydrological properties. Litter hydrological properties depend upon litter structure and its physical characteristics. Currently, previous studies were mainly focused on the comprehensive hydrological effects of the mixture litter or litter layers of different forest types and communities, including retention of the rainfall, evaporation and drought in soils, overland flow, rain splash erosion, and soil and water conservation, etc. However, the detailed nature process and mechanism of the litter hydrological process for single leaf have not been investigated. Furthermore, relationships between the litter properties and its hydrological capacity and decomposition have not been properly examined either.In this study, fresh leaf litter of 60 species was used as experimental material, which was selected in limestone and sandstone regions, Chongqing. Water-dipping and air-dry experiments were taken in laboratory to measure the leaf litter hydrological properties. Litter properties, including leaf tensile strength, litter SLA and litter LDMC, were also measured. The results showed that:1) There were no significant differences of the maximal water content per litter mass between different regions, while the maximal water content per litter area in limestone region was significantly higher than it in sandstone region(P<0.05). The maximal water absorption rate of litter in limestone regions was significantly higher than that in sandstone regions. And 80% species (including trees and shrubs) from limestone area reached this rate in the pre-0.3h time of water holding process, while the sandstone was only about 50%. There were no significant differences of the maximal rate of water-loss per mass of the litter from different areas, but the maximal rate of water-loss per area of the limestone region litter was significantly higher than that of sandstone region litter. More than 90% species’water-losing rate reached zero after 18h of air-dry process. The relative water content (RWC) and natural moisture content (NMC) of the litter from limestone area were both significantly higher than those from sandstone area. It concluded that litter from limestone region had stronger water holing capacity than that from sandstone region, and litter from limestone region had rapid water absorption capacity at the earlier stage of the water holding process (0-1h); At the earlier stage of the water holding process, litter water holding capacity mainly depended on litter surface, while the later depended on dry matter content which was more related to the eventual water content, specially to the litter from limestone region; The differences of litter water-holding capacity among different life-form plants were mainly related to litter surface hydrological property.2) Litter SLA was significantly positively correlated with maximal water content per unit mass, maximal water absorption rate per unit mass and maximal water-loss rate (P< 0.01). Litter LDMC was significantly negatively correlated with maximal water content per unit mass, maximal water absorption rate per unit mass, maximal water-loss rate per unit mass and natural moisture content (P < 0.01). And the relationships of sandstone litter between litter hydrological properties and litter traits were always stronger than that of limestone litter. In sandstone region, litter NMC was significantly positively correlated with maximal water content per unit mass and maximal water absorption rate per unit mass (P< 0.01); litter RWC was significantly negatively correlated with maximal water content per unit mass (P< 0.01). But in limestone region, litter NMC was significantly positively correlated with maximal water content per unit area and maximal water absorption rate per unit area (P< 0.05), while RWC was significantly negatively correlated with them (P< 0.01). Litter hydrological properties were significantly negatively correlated with leaf tensile strength, which function relationship was:y=axb. Litter water-holding property was significantly positively correlated with water-losing characteristics, and function relationship was: y=axb.3) Litter hydrological properties had significant correlation with litter decomposition traits, and plant litter hydrological characteristics from different regions and life forms had different relationships with litter decomposition traits. Natural moisture content of litter form different regions and life forms (expect shrubs) showed a highly significant correlation with the decomposition traits (P<0.01). Furthermore, the relationship between litter decomposition ratio and natural moisture content of herbaceous litter was stronger than that of the trees; the correlation intensity of litter from different regions between natural moisture content and litter decomposition ratio had little difference (R2=0.46,0.47). Leaf litter surface water-holding capacity has a significant positive correlation with litter decomposition ratio, no significant correlation with decomposition rate. The results shown that: the hydrological properties of litter and decomposition had a highly significant positive correlations; effects of hydrological properties (water holding capacity) on the decomposition were strong at earlier stage of decomposition; litter hydrological properties of the limestone region had a stronger significant effect on the litter decomposition than that of sandstone region; and hydrological properties of herbaceous had stronger effect on litter decomposition than that of trees.