Effects Of Planting Hardwood Species Under The Canopy Of Masson's Pine Stand On The Forest Litter And Soils

Masson's pine (Pinus massoniana) is one of the major timer tree species in Fujian, which covers about 43.6% of the total afforested area. However, long-term management of monoculture plantations was found to cause soil degradation and productivity decline. In the meanwhile, large area of single species stands created an environment easily being infected by Dendrolimus punctatus and attacked by wild fire, which threatened the sustainable development of forestry. Therefore, establishment of mixed forests is the key for solving these problems, and changing the pure coniferous stands into mixed forest appears to be more practical and important, providing an effective way for remedying this kind of fragile ecosystem. A large number of studies have been focused on Masson's pine forest management, but very few concerned with multiple mixed stand patterns on one site. Since the middle of 1980's, Xinkou Experimental Forest Farm of Fujian Agriculture and Forest University has started to plant hardwood species, including Michelia macclurei, Castcmopsis fissa, Castanopsis sclerophylla, Castanopsis kawakmii, Cyclobalanopsis myrsinaefalia, and Castanopsis lamontii, under the canopy of Pinus massoniana plantations. After sixteen years of development, six types of uneven-aged mixed stands were formed. Through three years of located studies, the effects of interplanting hardwood species under the canopy of Masson's pine plantations on forest litter and soils were analysed and discussed.The major results are as follows:I. Annual litterfall in pure Pinus massoniana stand was 3.44 t hm² and annual litterfall in six mixed forests by inter-planting with Michelia maclurei, Castanopsis fissa, Castanopsis sclerophylla, Castanopsis kawakamii, Cyclobalanopsis myrsinaefolia andCastanopsis lamontii amounted to 7.14 t hm"2, 6.74 t hm"2, 8.04 t hm'2, 7.15 t hm"2, 7.53thm"2 $16.15 t thm"2, respectively. Seasonal dynamics of litterfall in the mixed stands showed binomial patterns, with the first peak occurring between February and April, the second occurring in August or September. The leaffall in litter composition in all the six stands amounted for 50%⁷1% of the total. The proportion of the others was different obviously and decreased in the order: branches>miscel!aneous>bard>fruit. In the mixed forests, 50-80% of the total litterfall comes from Pinus massoniana tress, 42⁵0% from the respective hardwood tress, with significant difference existing between their litter composition.2. Analysis of nutrient of litterfall showed annual nutrient return amounts from forest litterfall were, respectively, 204.95 kg hm"2, 223.93 kg hm"2, 304.12 kg hm"2, 288.46 kg hm"2, 213.77 kg hm"2, 238.05 kg hm"2, for the above six mixed communities, and 142.01 kg hm'2 for pure Pinus massoniana stand.3. The biomass of forest litter were , respectively , 9.39, 11.99, 6.97, 12.72, 15.57, 8.45, 5.02 t hm'2, of which litter in L layer made up of 73.2%, 51.3%, 85.4%, 61.0%, 59.5%, 47.2% and 86.2%, respectively, averaging 63.3%. Significant differences in nutrient concentrations existed between forest communities and litter components, but the elements consistently revealed the same trend, decreasing in the order: Ca>N>Mg or K>P. Total nutrient accumulations in the mixed forest floor ranged from 174.22³67.00 kg hm'2, and was 130.05 kg hm"2 in the pure stand. The result showed it was good to increase the accumulations in the ecosystems interplanting hardwood under the Pinus massoniana plantation.4. Based on the comparative withered and fallen amount accumulation(biomass of litterfall) and fallen rates(annual litterfall), the litter turnover time in seven communities was 1.15, 0.97, 0.84, 1.17, 1.42, 0.76 and 1.52 a. Further analysis on litter composition showed the turnover time of the branchfall was longer than that of the leaffall and the branchfall and...