Hydrological Characteristics And Nutrient Elements In Litter Of Common Tree Species In Changchun

Forest litter plays an important role in dispersing precipitation,slowing surface runoff and nutrient cycling.Studying the eco-hydrological functions and nutrient characteristics of urban forest litter is beneficial to maintaini ng and enhancing the ecological functions of urban forest such as soil fertility and soil and water conservation.In this study,a combination of field survey and indoor experiments was used to investigate the hydrological characteristics of different deco mposition layers and the differences in nutrient contents in 14 common tree species in Changchun,in order to provide a scientific basis for screening high-quality water-conserving forest in Changchun and investigating the role of urban forest litter in the nutrient cycle of the ecosystem.The main results of the study are as follows:(1)Among the 14 common tree species in Changchun,the total accumulation of litter in the Korean Spruce(Picea koraiensis Nakai.)forest was the highest,followed by the Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest.The total a ccumulation of the Mongolian oak(Quercus mongolica Fisch.)forest was the hi ghest among broad-leaved forests at 11.79t/hm~2 and was significantly higher th an that of other broad-leaved forests(P<0.05).Except for the Mongolian oak(Quercus mongolica Fisch.)forest,the total accumulation of coniferous forest was significantly higher than that of broad-leaved forest(P<0.05).(2)The maximum water holding rate in the un-decomposed layer was significantly higher(P<0.05)in both the Kyoto Peach(Amygdalus persica L.)forest and the Asian White Birch(Betula platyphylla Suk.)forest stands than in other stands,while it was significantly lower(P<0.05)in coniferous stands than in broad-leaf stands,except for Xing’an Larch(Larix gmelinii(Rupr.)Rupr.)forest,which had the lowest maximum water holding rate among broad-leaf stands.The maximum water holding capacity in the un-decomposed layer was the highest in the Mongolian oak(Quercus mongolica Fisch.)forest,which was 7.58 times higher than the lowest value in the Purple Linden(Tilia amurensis Rupr.)forest,and also significantly higher than other forest stands(P<0.05).The water holding capacity of the decomposing layers showed a trend of increasing and then stabilizing with the increase of water immersion time,which generally showed a rapid increase from 0 to 2 h,a steady increase from 2 to 12 h,and a stable state of saturation from 12 to 24 h.Except for the Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest and the Korean Spruce(Picea koraiensis Nakai.)forest,there was a power function of R=at~bfor the water holding rate and water immersion time of litter in different decomposition layers,and a power function of W=at~bfor the water holding rate and water immersion time in each stand.And the fit was high,indicating that there was a high correlation between the water holding rate and amount of litter,and the immersion time in each stand.The correlation between the water holding rate,water holding volume,and immersion time in the Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest and the Korean Spruce(Picea koraiensis Nakai.)forest was Y=alnt+b,and the fit was relatively high.(3)The water loss of litter at each moment was proportional to the air-drying time,and the water loss increased with the increase of air-drying time.The dynamic changes of water loss in different layers of litter within 24 h and wind-drying time were generally consistent,showing a rapid increase from 0 to 8 h,a steady inc rease from 10 to 12 h,and a stable state of saturation from 12 to 24 h.However,the water loss in the semi-decomposed layer of the Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest was close to a linear increasing trend.The maximum water loss in the semi-decomposed layer of litter was the highest in the Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest,reaching 17.73t/hm~2,which was also the highest water loss in the two decomposed layers of each stand.The maximum storage capacity of each stand in the un-decomposed layer was Mongolian oak(Quercus mongolica Fisch.)forest,Korean Spruce(Picea koraiensis Nakai.)forest,Sand Fir(Abies holophylla Maxim.).forest,Asian White Birch(Betula platyphylla Suk.)forest,Siberian Apricot(Armeniaca sibirica(L.)Lam.)forest,Xing’an larch(Larix gmelinii(Rupr.)Rupr.)forest,Ginkgo(Ginkgo biloba L.)forest,Kyoto Peach(Amygdalus persica L.)forest,Purple-leaved European Bird Cherry(Padus avium Mill.)forest,Mongolian Scotch Pine(Pinus sylvestris L.mongolica Litv.)forest,Chinese Pine(Pinus tabuliformis Carr.)forest,Silver Yang(Populus alba L.)forest,Dry Willow(Salix matsudana Koidz.)forest,and Purple Linden(Tilia amurensis Rupr.)forest.In the semi-decomposed layer,the maximum interception of coniferous forests was significantly higher than that of broad-leaved forests,except for Sand Fir(Abies holophylla Maxim.),Korean Spruce(Picea koraiensis Nakai.),and Mongolian oak(Quercus mongolica Fisch.)forests(P<0.05).(4)The litter of accumulation about broad-leaved forests,especially Mongolian oak(Quercus mongolica Fisch.),Asian White Birch(Betula platyphylla Suk.),Ky oto Peach(Amygdalus persica L.),and Siberian Apricot(Armeniaca sibiric a(L.)Lam.)forests,maintained a strong water-holding and retention capacity at low levels.Among coniferous forests,Korean Spruce(Picea koraiensis Nakai.)and Sand Fir(Abies holophylla Maxim.)forests have high accumulation and good water retention capacity,while the water loss characteristics are not outstanding.(5)The nutrients enriched in each decomposing layer of litter in different stands were mainly N and K elements,followed by Na,Ca and Fe elements.The content of N element in the litter of each stand generally increased with the increase of decomposition,which was an enrichment pattern.The highest nutrient content of litter in different decomposition layers was N element.The content of K element decreased gradually from non-decomposing to semi-decomposing layers in all stands,except for Purple Linden(Tilia amurensis Rupr.),Ginkgo(Ginkgo biloba L.),Chinese Pine(Pinus tabuliformis Carr.)and Sand Fir(Abies holophylla Maxim)forests.The Fe content increased with decomposition in broad-leaved forest,except for Dry Willow(Salix matsudana Koidz.)forest,while in coniferous forest,the Fe content accumulated from non-decomposed to semi-decomposed layers,except for Sand Fir(Abies holophylla Maxim.)and Korean Spruce(Picea koraiensis Nakai.)forests.The Ca content decreased with the deepening of decomposition of litter in all stands except Xing’an larch(Larix gmelinii(Rupr.)Rupr.)and Korean Spruce(Picea koraiensis Nakai.)forests.In contrast,the Na content of litter in 14 forest stands did not show a certain regularity.