The Effect Of Forest Landscape Restoration On Key Ecological Functions In The Zagunao Watershed,the Upper Reaches Of Minjiang River

The subalpine forests in the upper reaches of the Minjiang River provide important ecosystem services including hydrological regulation and soil conservation for the upper reaches of the Yangtze River basin as well as the middle and lower reaches of the Yangtze River basin.The forest in region experienced large-scale logging in the early1960s,resulting in the depletion of natural forest resources.Due to harsh environment,human impact and global climate change,forest ecological functions in this region were severely degraded.As a key area for Natural Forest Protection Projects,the forestry sectors have implemented a series of forest restoration measures since the 1990s.Understanding the effect of the forest restoration measures on forest landscape structure and ecosystem functions such as carbon sequestration and water conservation is essential for natural resource management.Thought ecohydrological models can be used in evaluating hydrological functions of forest ecosystems,they lack the simulation of forest succession and growth.Forest landscape models are for simulating forest succession and growth dynamics,but without the module for modeling the hydrological process of a forest ecosystem.Therefore,current techniques fail to meet management demands for evaluating the effect of forest restoration on forest structure and functions.In this study,we selected the Zagunao watershed as an example to assess the effect of forest restoration measures on the forest landscape successions and associated key ecological functions including carbon sequestration and water conservation in a changing climate by a combined used of the forest landscape model LANDIS PRO and water conservation quantification method.LANDIS PRO model was firstly used to simulate and predict the long-term?2010-2060?effects of forest restoration scenarios?natural and artificial restoration?on the forest landscape under future climate scenario.Then,based on the simulation of above-ground biomass by LANDIS PRO,the dynamic changes of forest carbon sequestration were evaluated.Finally,based on the simulation of forest landscape restoration by LANDIS PRO and the established water conservation function parameter database,the dynamic changes of water conservation function of the forests under two forest restoration scenarios in the study watershed are assessed by use of the integrated storage capacity method.The main results are:?1?According to the initialization results of model,the species information simulated by the model is consistent with the field survey data.The forest above-biomass estimated by variable BEF?Biomass Expansion Factor?method is basically consistent with the model prediction.Therefore,the forest landscape map calibrated by the field survey data can represent the forest composition and structure in2010 in the study watershed.?2?According to the simulation results of model,the forest composition changed significantly on both spatial and temporal scales after the implementation of forest restoration measures.The average forest BA?Basal area?of Picea asperata Mast increases significantly from 2050 to 2060 while the average BA of Abies faxoniana increases significantly in the early and later years.The forest BA of Pinus tabuliformis increases significantly at the beginning and the end of the study period?P<0.05?.The average forest BA of Quercus semicarpifolia decreases insignificantly?P>0.05?while that of Betula platyphylla and Larix gmelinii forests show a significant downward trend at the beginning and the end of the study period,respectively.Under the artificial forest restoration scenario,the distribution of Abies faxoniana expands in arid river valley,northern slope,and alpine regions,while it's the distribution area in the southern slope region decreases.The distribution area of Picea asperata Mast increases in arid river valley and southern slope regions,while its distribution area in northern slope and alpine regions shrinks.The distribution area of Betula platyphylla and Larix gmelinii show a decreasing trend on different land types.Artificial forest restoration measures are favorable for the forest succession to the climax community in the study area.?3?The quantitative results of forest key ecological functions show that the forest landscape restoration has insignificant effect on the forest water conservation function in the early years,while a significant improvement in water conservation function is estimated at the end of study period.In the artificial restoration scenario,the implementation of forest restoration measures resulted in a reduction of forest AGB and water conservation function in the early and middle study periods?2010-2040?,which are lower than that in natural restoration scenario during the same period.However,by2050,the forest water conservation capacity in the artificial restoration scenario is 14.32%⁵4.07%higher than that in the natural restoration scenario.The Above-ground biomass in the artificial restoration scenario in 2060(44.66 Mg·hm^-2)exceeds that in the natural recovery scenario(35.14 Mg·hm^-2).?4?In general,artificial forest restoration measures are favorable for the forest succession to the climax community in the study area,which can effectively improve the key ecological functions of the subalpine forests.These restoration measures enhance the ecological resilience of forest ecosystem to adapt climate change.The findings are of great significance to the adaptive management of forest resources and water resources in the context of climate change.