Knowledge of soil respiration and the influencing factors in desert ecosystems is essential to understanding carbon dynamics and responses of biotic and abiotic processes in soils to climate change. In this study, soi...Knowledge of soil respiration and the influencing factors in desert ecosystems is essential to understanding carbon dynamics and responses of biotic and abiotic processes in soils to climate change. In this study, soil respiration rate（R_s） for three land-cover types（shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land） in the hinterland of the Taklimakan Desert was measured in May 2015 using an automated soil CO_2 flux system. The effects of soil temperature（T_s） and soil water content（W_s） on R_s were also analyzed. The results showed that R_s values in shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land were all low and exhibited obvious diurnal fluctuations. The establishment of straw checkerboard barriers in sandy land had no significant effect on R_s, while the establishment of shelterbelts significantly increased R_s. Shifting sandy land and sandy land with straw checkerboard barriers were carbon sinks at night and early morning and were carbon sources in the daytime, while shelter forest land always acted as a carbon source during the whole day. The synergistic effect of T_s and W_s could better explain the diurnal dynamics in R_s than single factor. In shifting sandy land and sandy land with straw checkerboard barriers, W_s was identified as a limiting factor influencing the diurnal dynamics of R_s. Furthermore, a relatively strong hysteresis loop existed between R_s and T_s. In contrast, in shelter forest land, R_s was significantly influenced by T_s, and a relatively weaker hysteresis loop existed between R_s and W_s.展开更多
The optimum models for cultivationg the seedlings of Dahurian Larch (Larix gmelim Rupr. ) were studied in the central nursery of Tahe Forestery Bureau from 1989 to 1993. The resultswerc as follows The optimum...The optimum models for cultivationg the seedlings of Dahurian Larch (Larix gmelim Rupr. ) were studied in the central nursery of Tahe Forestery Bureau from 1989 to 1993. The resultswerc as follows The optimum models of the main morphological standards of the seedlings were30000 kg /hm2 of' decomposed' ash for improviong soil, 70,000 kg/hm2 of excrement and 1,500 kg/hm2of' calcium superphosphate as basal fertilizer , and 500 kg/hm2 of (NH4)2HPO4 and 220 kg/hm2 of'urea as top dressing. During growth perlod of the seedlings, the growth was greatly checked when thesoil water suction (SWS) was uithin 50 ~ 73. 3 kPa or below 10 kPa but greatest when SWS waswithin 30 ~ 40 kPa in initial growth stage and within 10-20kPa in last growth stage. The method for determining the optimum sowing time is to measure the depth of soil thawing, accumulated temperature abovc 5℃ both at 5 cm of the depth of of soil and in atmosphere. In Tahe region, the optimumsowing trme for Dahurian larch for Dahuria larch is about on May 10 when the depth of soil thawing, the accumulatedtemperature above 5℃ at 5 cm of the depth and the accumulated temperature above 5℃ in atmosphere reaches 40 cm. abovc 46℃ and abovae 56℃ respectively. The optimum seedlings density forthis region is 600-800 individuals/m2.展开更多
基金funded by the National Natural Science Foundation of China(41175140)the National Department of Public Benefit(Meteorology)Research Foundation(GYHY201306066)
文摘Knowledge of soil respiration and the influencing factors in desert ecosystems is essential to understanding carbon dynamics and responses of biotic and abiotic processes in soils to climate change. In this study, soil respiration rate（R_s） for three land-cover types（shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land） in the hinterland of the Taklimakan Desert was measured in May 2015 using an automated soil CO_2 flux system. The effects of soil temperature（T_s） and soil water content（W_s） on R_s were also analyzed. The results showed that R_s values in shifting sandy land, sandy land with straw checkerboard barriers, and shelter forest land were all low and exhibited obvious diurnal fluctuations. The establishment of straw checkerboard barriers in sandy land had no significant effect on R_s, while the establishment of shelterbelts significantly increased R_s. Shifting sandy land and sandy land with straw checkerboard barriers were carbon sinks at night and early morning and were carbon sources in the daytime, while shelter forest land always acted as a carbon source during the whole day. The synergistic effect of T_s and W_s could better explain the diurnal dynamics in R_s than single factor. In shifting sandy land and sandy land with straw checkerboard barriers, W_s was identified as a limiting factor influencing the diurnal dynamics of R_s. Furthermore, a relatively strong hysteresis loop existed between R_s and T_s. In contrast, in shelter forest land, R_s was significantly influenced by T_s, and a relatively weaker hysteresis loop existed between R_s and W_s.
文摘The optimum models for cultivationg the seedlings of Dahurian Larch (Larix gmelim Rupr. ) were studied in the central nursery of Tahe Forestery Bureau from 1989 to 1993. The resultswerc as follows The optimum models of the main morphological standards of the seedlings were30000 kg /hm2 of' decomposed' ash for improviong soil, 70,000 kg/hm2 of excrement and 1,500 kg/hm2of' calcium superphosphate as basal fertilizer , and 500 kg/hm2 of (NH4)2HPO4 and 220 kg/hm2 of'urea as top dressing. During growth perlod of the seedlings, the growth was greatly checked when thesoil water suction (SWS) was uithin 50 ~ 73. 3 kPa or below 10 kPa but greatest when SWS waswithin 30 ~ 40 kPa in initial growth stage and within 10-20kPa in last growth stage. The method for determining the optimum sowing time is to measure the depth of soil thawing, accumulated temperature abovc 5℃ both at 5 cm of the depth of of soil and in atmosphere. In Tahe region, the optimumsowing trme for Dahurian larch for Dahuria larch is about on May 10 when the depth of soil thawing, the accumulatedtemperature above 5℃ at 5 cm of the depth and the accumulated temperature above 5℃ in atmosphere reaches 40 cm. abovc 46℃ and abovae 56℃ respectively. The optimum seedlings density forthis region is 600-800 individuals/m2.
